The Digest of UK Energy Statistics (DUKES) 2026 [‘Accredited official statistics’] was published 30 July. This updates the UK’s energy ‘transition’ story through end December 2025. “If you require supporting data tables please refer to the DUKES table of tables”. “DUKES_2025_table_of_tables.pdf” is the download file full of links.

Specifically, I was interested in DUKES 6 “Renewables”:

… because I use whole-year data from DUKES to adjust the energy totals from Gridwatch to more-closely match the numbers from the ‘accredited official statistics’.
[But read on to see the reservations I have with some of these official numbers.]

My last detailed post using DUKES-based adjustment factors was ‘400 Days on the ‘Renewable’ GB Grid’ was in February this year. Following this latest update of DUKES 6, I’ve re-visited whole-year 2025; and gone on to extrapolate from that real weather-dependent data to where GB power generation might be in a few years’ time.

GB ‘Renewables’

First, it’s worth dwelling for a moment on the sheer numbers of ‘renewable’ generation ‘stations’ of all sizes across our islands.

Fig 0: DUKES 6.7 Number of renewable electricity generating stations:

Focussing only on the weather-dependent sources:

• Nearly 10,000 Onshore Wind

• 54 Offshore Wind

• A bit over 2,000,000 Solar installations

As I’ve said before, that’s one heck of a weather-sampling system!

So, what performance do we get out of all those sources?

Figure 1: DUKES 6.3 Load factors for renewable electricity generation:

[note 1] “Percentage of how much was generated compared to maximum possible generation - based on the average of capacity at the start of the year and capacity at the end of the year.”
[note 2] “Percentage of how much was generated compared to maximum possible generation - based on the generation of sites whose capacity did not change throughout the year.”
Take your pick which basis you prefer - so far as I can tell, our provider of ‘accredited official statistics’ gives no hint which they think might be more valid.

For this post I’ve calculated the 6-year averages and the standard deviations 2020 - 2025. It’s clear from the numbers that ‘Wind’ is a meaningless category: Offshore Wind performance is distinctly different from that of Onshore Wind.

The [Mean - 2 Std. Devs] numbers should provide load factors we can probably achieve 95% of weather years. That is, load factors which aren’t hopelessly optimistic:
Onshore Wind 22.1 [note 1 basis, is virtually the same as 22.0 on note 2 basis];
Offshore Wind 32.6 [average of note 1 and note 2 basis];
Solar 9.1 to 9.6 [depending on which basis you prefer, note 1 or note 2]

What this means in practice, is that a new ‘renewable’ facility with a capacity of, say, 100 MW [should always be written as 100 MWp to signify that’s it maximum possible power output on the best weather day - see Figure 1A] will probably provide:
20 MW to 30 MW on average if it’s Onshore Wind;
30 MW to 50 MW on average if it’s Offshore Wind;
and about 10 MW on average if it’s Solar;
all while minimum power from each of these techs is zero, or close to it.

Figure 1A: The UK Wind Map with Less Dishonest Key:

So, according to the accredited official statistics, how much energy did we actually get from our huge fleet of ‘renewable’ generators in whole-year 2025? Let’s interrogate DUKES 6.2.

Figures 2A, 2B, 2C: DUKES 6.2 Capacity of, generation from renewable sources and shares of total generation:

As in previous years, [note 6] states the fairly meaningless but anyway over-optimistic sole “Wind” de-rate factor 0.43; and the absurdly high PV capacity de-rate factor 0.17. Compare these numbers with those in the DUKES 6.3 section of these ‘accredited official statistics’.

It’s occurred to me as I compile this post, that [note 8] referencing use of “a typical load factor” to derive estimates of ‘actual generation figures’ leads to a ‘chicken and egg’ conundrum. Do we know these are NOT the same “typical load factor”s as appear in [note 6] in Figure 2A. How can our provider of ‘accredited official statistics’ use “typical load factor”s to estimate one or more of the Generation figures without telling us:
- which ones?
- what is their estimate of the error range(s) in which numbers?
In fact, what distinguishes these ‘accredited official statistics’ from WAGs [wild-assed guesses]?

Given my doubts about the numbers DUKES 6 presents, I wonder: is it valid for DUKES to use any of those numbers in deriving their published percentages of the various forms of ‘renewable’ energy? Equally, is it valid for me to use the total 2025 electricity generation (GWh) from row 71 to derive my Demand adjustment factor for the Gridwatch data? Or the 2025 Wind total GWh from row 29, or the 2025 Solar total GWh from row 33, for those adjustment factors?
Despite these doubts, I estimated the adjustment factors shown in Figure 3A.

Whole-year 2025 [adjusted Gridwatch data basis].
[Note: Gridwatch data was missing for almost exactly three days, from 19.05 on 17Mar 2025, to 19.20 on 20Mar 2025. I’ve adjusted whole-year totals pro-rata, but that gap obviously introduces small uncertainties.]

Figures 3: Whole-Year 2025, Adjusted Gridwatch Data:

Figure 3B focusses on the [fossil-free] Shortfalls (the red plot) through the year, and shows the net Import (+ve) / Export (-ve) power (purple plot) to give a direct visual comparison of magnitudes.

The worst [fossil-free] Shortfalls were off the chart: more than -50,000 MW in January 2025.

What might NESO’s future massive expansions in Wind and Solar capacities bring? [Assuming they can be usefully connected to the parts of the country where the Demand is located, which, judging from Constraint / Curtailment costs (£1.8bn in 2025), is a massive assumption.]

Extrapolation: the Future Expanded Wind and Solar Fleets

I used to spend too long trying to decipher NESO ‘pathways’ to figure out what multiples of generated Wind GWh and of generated Solar GWh I should use in my extrapolations. [Let alone how to allocate Onshore versus Offshore Wind multiples, or how much improvements in the different technologies might increase future Load Factors.]

I’ve never found anything from NESO that explains their reasoned thinking behind the future load factors they use1, so I decided to give up over-thinking it.

Instead, I’m using the same future multipliers as the last time I attempted the exercise:
- Future Demand = current Demand times 1.110; [allows for increased electrification]
- Future Wind = current Wind times 2.976; [near as dammit 3 times!]
- Future Solar = current Solar times 3.096; [near as dammit 3 times!]

Then simply using these multiples of the power generated each 5-minute interval by each ‘renewable’ technology [holding Nuclear and Imports/Exports the same] gives us Figure 4.

Figure 4: Future GB Power Generation based on Whole-Year 2025:

The [potential] Surplus plot in grey shows the power that would have to be Curtailed / Constrained to balance Generation = Demand to keep the grid from collapse. [Unless new Demand able to cope with the extreme variability evident in the grey plot could be added to the GB grid.]

In this future scenario, the worst Shortfalls are of round -55,000 MW in January.

See also the charts included at Figures 2A in my “400 Days…” post. There, I estimated the electrical energy storage required to get GB through that extended winter lull as around 7,920,000 MWh ≈ 870 times the Dinorwyg pumped hydro energy storage scheme or ≈ 13,000 times the Thurrock Storage BESS.

Energy Storage to the Rescue, Then?

Ofgem’s ‘minded to’ long duration energy storage scheme list was published 26 June 2026:

ModoEnergy then published their assessment of Likely Future Electrical Storage that might result, and over what timescale: ‘firm’ 2,600 MW / 56,000 MWh by 2035.

Note the ‘firm’ green part of the plot only jinks upwards in 2030.
So much for this ‘minded-to’ storage helping to achieve ‘Net Zero’ by [the end of] 2030!

But let’s see what difference that extra 56 GWh by 2035 might make [ignoring the power flow limit ± 2,600 MW for simplicity]:

Figure 5: Future GB Power Generation with ‘Minded to’ LDES [~2035]:

The worst-case [fossil-free] Shortfall is -4,571 MWh per 5 mins = 54,850 MW. Note this occurs at the end of a long lull during which the LDES has gone completely flat. Hence all that future LDES does not reduce that requirement for 54,850 MW of separate dispatchable generation capacity one iota.

Which was the conclusion I reached in relation to the Australian grid in my recent “Batteries to the Rescue?” post. Following which, commenter TytoWatt suggested fossil-fueled assets should be run to charge up energy storage in such a lull.

Which subsequently made me think: isn’t this simply an argument for more low-carbon base-load generation? For example, if GB had another 10 or 20 GW of reliable zero-carbon generation, that would close the gap. [Now if only nuclear wasn’t so ludicrously expensive and absurdly slow to build in the UK…]

Ok, so, not Storage. Interconnectors to the Rescue?

Not from Norway, by the looks, and hence also less likely from Denmark and Germany [which currently receive Norwegian ‘green’ hydro power via their interconnectors].

Remember too, we often share uncooperative weather conditions with multiple neighbouring territories, whether in hot sunny times of the year, or in winter.

I conclude that GB will need 55 GW = 55,000 MW of our own dispatchable generation to avoid descending into ‘renewable’ darkness multiple times in a typical year.

#KeepTheLightsOn

Copyright © 2026 Chris S Bond

Disclaimer: Opinions expressed are solely my own.

This material is not peer-reviewed.

I am against #GroupThink.

Your feedback via polite factual comments / reasoned arguments welcome.

Introduction

My last post “Energy ‘Transition’ on the NEM” was based on just over two years of ½-hourly power generation data from the Eastern Australia power grid (the NEM). In it I identified two deep NEM-wide Wind lulls: in June 2025 and again in June 2026. I plotted these in Figures 4A and 4B, repeated below.

Figure 4A: Combined NEM Wind, 14 Days in June 2025:

Every evening from 26 June 2025 for the next 8 days the worst [fossil-free] Shortfalls were 26 GW to 24 GW - the measure of dispatchable power needed to keep the lights on at times of most stress on the NEM grid.

Figure 4B: Combined NEM Wind, 14 Days in June 2026:

A year later the worst [fossil-free] Shortfalls were 25 GW to 23 GW for 6 days from 21 June 2026.

I’ve since become aware of the ABC article of 27 June 2026: “Electricity price spikes and batteries drain as wind drought tests green flag-bearer”.1

That ABC article went on to quote South Australia Energy Minister Tom Koutsantonis talking about “significant volumes of long duration" storage, citing “2,500 megawatts, which would be able to power about 300,000 homes for eight hours.” So that’s 2,500 MW x 8h = 20,000 MWh.

How much difference would that make? I wondered. Very difficult to answer just for South Australia because of its interconnections with other parts of the NEM grid.

So, in this post I explore the possible benefits of electrical energy storage for the whole NEM, using recent NEM ½-hourly data as the basis. I’ve extrapolated to some possible ultimate future cases where the NEM’s energy ‘transition’ is largely complete, varying the electrical energy storage quantity available.
The physics constraint I obey throughout is: Supply must = Demand 60/24/365
I assume that future grid capacity would be increased to accommodate the multitude of ‘renewable’ generators, energy storage systems, etc. etc. across the NEM.

First, to illustrate the context.

Energy Storage for the Sunniest Day (so far) on the NEM

It’s useful to appreciate the magnitude of Solar generation [rooftop + Utility] across the NEM. To that end, I’ve estimated the electrical energy storage capacity needed to capture all Solar power recorded in ½-hourly NEM data for “The Sunniest Day Yet in Aus” . The salient parts from that post are repeated below, edited slightly for clarity and to bring it up to date:

A new Solar generation record [was] set 09 December 2025, 00:00 thru 23:59 h:

• Total electrical energy from Solar [rooftop + Utility]: 222,329 MWh

• Peak cumulative Solar power across the NEM region: 23,555 MW

• [minimum cumulative Solar power across the NEM: 0 MW, because nights]

Should the NEM wish to smooth this huge surge of power using just battery energy storage systems (BESSs), around 135,000 MWh of [net, usable] energy storage capacity would be required...

That’s ≈ 80 times the [recently brought back on-line] Waratah Super Battery, which had a total project cost of ≈ AUD 1 billion2

Figure 0: Energy Storage to Smooth Power through the Sunniest Day:

The Figure 0 charts show a 24-hour rolling simulation of power flows in MW (plotted against the left axis) and the necessary energy to be stored in MWh (plotted on the right axis). I assigned the round-trip efficiency (RTE) of 85% which is in the ball-park of RTEs actually exhibited by the BESS systems of the NEM States. [Pumped Hydro energy storage (PHES) probably has a RTE of around 75% but let’s not nit-pick.]

I adjusted the initial state of charge (SoC) so as to keep the minimum SoC above 10%. The BESS capacity needed to keep maximum SoC to around 90% is ~ 1.1 maximum SoC experienced by the cumulative future BESS. [That initial SoC assumes that prior to this day there was sufficient ‘renewable’ generation that the BESS system could be charged up.]

The Solar energy (MWh) that was generated across the NEM on that very sunny day, if averaged across 24 hours, would be a power of 9,264 MW. The plots in Figure 0 assume that that constant power is maintained, either from discharge of the BESS, or from surplus Solar while the BESS re-charges. [Of course, to accommodate variations in Demand, the NEM would likely vary BESS discharge rates, but that would be a simple scheduling issue IF the necessary capacity of BESS was available. The financial side may not be so simple.]

That BESS capacity of 135,000 MWh is about 80 times the energy storage capacity of the Waratah Super Battery. The maximum BESS power flow in this simple simulation is 14,291 MW or around 17 times the 850 MW power rating of Waratah [or around 7 times the Snowy2.0 pumped hydro scheme power capacity].

The energy lost by the [assumed 85%] RTE of the BESS systems is nearly 20,000 MWh in that day. This indicates how much Wind generation would be needed across even the sunniest day to prevent the BESS from running down.

Of course, other forms of energy storage might become commercially available and, hopefully, more affordable: for example, compressed air, liquefied air, flow batteries, etc.3 See for example the 'minded to' consultation by the UK’s Ofgem of 26 June 2026. Other than pumped hydro, each has its potential, yet-to-be-proved-at-scale pros and cons.
Pumped hydro schemes like Snowy2.0 have well-known technical performance, including that the ‘charging/discharging’ power ratings are fixed by the design of the massive machines involved. So you would need a multiple of them to achieve the necessary MW power.
BESS and technologies not requiring special geography can be co-located with large generation facilities, probably with reductions in grid connection costs.

Extrapolation to the Future NEM

My extrapolation to a possible ‘decarbonised’ NEM future is similar to that espoused by DavidOsmond8 on X. Except:
- I allow for a 25% increase in Demand in the future case;
- I combine rooftop Solar and Utility Solar into just Solar;
- I don’t use perfect foresight to adjust my extrapolation - especially hydro - for future less-advantageous weather conditions;
- I definitely don’t fudge the question of what keeps the lights on by calling the mystery energy source that fills in [fossil-free] Shortfalls, ‘Other’;
- I absolutely refuse to use ‘Other’ to charge up batteries in anticipation of them going flat in the future because I don’t believe the NEM possesses a functioning crystal ball. Also because that would be a waste of [likely fossil] energy just to flatter batteries.

So, each of the scenarios that follow are based on the last year of real ½-hourly weather-dependent generation data simply extrapolated to a possible NEM future using the following main ‘scale factors’:
NEM Demand factor 1.25 to allow for population growth, electrification…
NEM Wind factor 4.375 [*]
NEM Solar factor 2.625 [*]
[*] each derived by multiplying Mr Osmond’s 22 July 2026 scale factors by 1.25.
All at AUD ???1 additional capital expense, plus AUD ???2 additional capital expense for associated grid reinforcement etc. etc.
And substantial portions of these capital expenses will recur every 15-25 years or so, depending how long the facilities take to wear out / become uneconomic / etc.

I make minor adjustments to the power from Hydro depending on the energy balance in the ½-hour interval before, while keeping the total MWh generated by Hydro across the year the same.

Mr Osmond’s suggested electrical energy storage requirement is derived by multiplying the annual average NEM Demand (MW) x 5 (hours). It’s a useful starting point, so with my 1.25 times increased Demand it comes to:
31,268 MW x 5 h = 156,000 MWh [round numbers]

Then I vary storage using multiples: ¼, ½, 1, 2, 4 and 8 times 156,000 MWh. Hence I map the potential benefits, and physics-imposed limits, of incremental energy storage.

Figures 1 provide the six whole-year scenario results. [To zoom, click on an image.]

Figures 1: Possible Future NEM Power Generation Scenarios:

Just scanning the charts in Figures 1 you get a sense of the diminishing returns [the reducing number of red Shortfall spikes] yielded by the increasing available energy storage [the grey plot]. The numbers below each plot show the numerical results.
Key results versus the energy storage capacity available each scenario are:

39,000 MWh: Shortfall 29.9% of ½-hours, 9.9% of Demand = 27.0 TWh / y;
Curtailed (physics): 57 TWh / y

78,000 MWh: Shortfall 21.9% of ½-hours, 7.6% of Demand = 20.8 TWh / y;
Curtailed (physics): 50 TWh / y

156,000 MWh: Shortfall 14.0% of ½-hours, 5.3% of Demand = 14.6 TWh / y;
Curtailed (physics): 42 TWh / y

312,000 MWh: Shortfall 10.3% of ½-hours, 4.0% of Demand = 11.0 TWh / y;
Curtailed (physics): 38 TWh / y

624,000 MWh: Shortfall 7.5% of ½-hours, 3.0% of Demand = 8.1 TWh / y;
Curtailed (physics): 34 TWh / y

1,248,000 MWh: Shortfall 5.7% of ½-hours, 2.2% of Demand = 5.9 TWh / y;
Curtailed (physics): 32 TWh / y

I took the series to a rather ridiculous extreme to demonstrate that physics limits the benefit of ever more storage. [I leave it to the reader to decide how far they think the economics might limit it.] It’s clear from the charts that funding of these technologies is going to get interesting: during benign summer weather, the electrical energy storage stays mostly full - possibly for weeks on end - with little energy flowing in or out. Absent additional new Demand [for example electrolysis to produce hydrogen, but see note 3] the ‘surplus’ must be curtailed to keep the grid stable. Yet despite all that storage, Shortfalls still occur during common winter Wind lulls. These require very substantial capacities of dispatchable generation to prevent the lights going out.

Which brings me neatly to the last questions I want to pose.

How much dispatchable generation will the future NEM need?
and
How much is that reduced by having more storage capacity?

Figures 2: Designing the NEM for the Worse Case:

I very deliberately used “Worse” not “Worst” in the heading for Figures 2 because I have no doubt the NEM has experienced many instances of less cooperative weather in the past, and will do again in future. This is just a very recent 6 weeks’ of data showing a key aspect of designing a weather-dependent power generation system.

The postulated fleet of future BESS would have gone completely flat THREE TIMES just in that 6 weeks. I drew the orange ellipses on the charts in my Excel workbook, and you can see it’s only in the last [ridiculous] storage scenario that the third Shortfall peak has gone. In all the other five scenarios the Shortfall peaks are all around -30,000 MW. That’s how much dispatchable power generation would be required across the NEM to keep the lights on during this worse weather. Regardless of how many BESS facilities are installed alongside all the Windmills and fields of Solar panels.

So, to answer my two questions above:

How much dispatchable generation will the future NEM need?
30,000 MW [at least] to #KeepTheLightsOn

How much is that reduced by having more storage capacity?
Not one iota even with ludicrously large quantities

Footnotes

• It’s often suggested that the solution is to get a smarter grid with, amongst other things, ‘demand management’. Sure, if you want to de-industrialise.

• I saw a LinkedIn post recently comparing quantities of waste generated by ‘renewables’ with other sources of waste. I note that the post only talked to Wind and Solar waste streams and NOT to BESS energy cell waste streams. I’d be grateful if anyone can point me to a public source of operational data for recycling energy cells - is it getting anywhere near ‘sustainable’?

• I’ve thought about doing a post on energy return on energy invested (EROEI) and whether data from the NEM [or from anywhere else] can yet show ‘renewables’ can power a thriving society. For example, perhaps we could isolate the South Australia grid from the rest of the NEM and see if it sinks or swims. But, apart from the objections from the citizens, I guess that currently there’s too much carbon imports in the form of China’s coal-powered ‘renewable’ products to be able to even begin the analysis.

• Thank you to Open Electricity. The latest list view of NEM operating BESS facilities I accessed 06Aug2026 no longer shows duplicate MWh for charging and discharging [thumbs up!] Consequently the total energy storage capacity of NEM facilities published by OE has dropped to 8,623 MWh … but I’m dubious that that’s correct because it’s the same number as given for the total power of facilities = 8,623 MW and we know that many of them are 2-hour or more. But an improvement [smiley!]

Postscript

I’ve collected another 7 days of ½-hourly NEM data since starting this post and, would you believe it? Another one of those rare-as-hens-teeth lulls just happened again! Not for quite as long, but equally devastating if all your hopes of keeping the lights on are pinned on BESS.

Figures 3A: Full Extrapolations for a Fourth Worse Case:

Figures 3B: The Last 50 Days Reveal a Fourth Worse Case:

Please feel free to share this post with South Australia Energy Minister Tom Koutsantonis.

Copyright © 2026 Chris S Bond

Disclaimer: Opinions expressed are solely my own.

This material is not peer-reviewed.

I am against #GroupThink.

Your feedback via polite factual comments / reasoned arguments welcome.

I’ve written multiple posts about Australia’s NEM, because it’s a live experiment on a continental scale. By that I mean it’s testing the theory that a modern, wealthy, industrialised territory can still #KeepTheLightsOn while it ‘transitions’ to generating a large majority of its power from ‘renewables’ alone.

I was planning to post an update about a month ago based on exactly 2 years of ½-hourly NEM data ending mid-June 2026. But then I saw numerous references on LinkedIn to a low-wind period the end of June 2026, so I continued collecting sets of data [7d x 30 minute intervals via Open Electricity] until 03:00 on 17 July 2026.

Open Electricity data has been expanded recently to include, for each NEM State, information on:
- Curtailment of Wind, and of Utility-scale Solar PV;
- Energy being stored in batteries, and energy being released from batteries.

So, for the data from the latter part of Year 2, I’ve looked at whether there is any obvious correlation between Curtailment and / or Battery traffic, and [fossil-free] Shortfall. Also, and specifically for energy ‘transition’ poster-child South Australia, I’ve looked at how Battery charging, Curtailment and Import / Export vary with [fossil-free] Shortfall.

Two Whole Years on the NEM

The overall pictures for mid-2024 to mid-2025 [Figure 1A] and mid-2025 to just after mid-2026 [Figure 1B] are presented below.

Figure 1A: NEM 2024-25: Demand, Solar, Wind and Shortfalls:

Figure 1B: NEM 2025-26.1: Demand, Solar, Wind and Shortfalls:

Figures 1A and 1B present just over two whole years of NEM power generation from mid-winter 2024 through high summer 2024-25 to the next mid-winter 2025, and again through to mid-winter 2026. The red [fossil-free] Shortfall plot for 2025-26 looks to have moved up slightly [i.e. slightly reduced Shortfalls] relative to that for 2024-25. That appears to be confirmed by the annualised totals:
2024-25 Shortfall = 126.1 TWh ;
2025-26 Shortfall = 120.8 TWh [annualised]

So, has the NEM made (126.1-120.8)/126.1 = 4.2% progress towards ‘Net Zero’ in the last year? I don’t know, because I don’t think just two years of data is sufficient for such precision. In particular, the difference between the annualised Shortfalls in each of the two years might be explained by there having been more benign weather recently. All I would be confident in saying is that it appears the direction of change is to a slightly lower-carbon grid.

I note that at no point in either year is ‘renewable’ generation meeting NEM Demand as a whole [which was 214.2 TWh/y in the earlier year and pro-rata 219.9 TWh/y in the later period]. In other words, there is currently never a surplus of ‘renewable’ generation across the NEM. It follows that electrical energy being sent to battery storage over these two years must have been largely derived from fossil generation.

I also note that the deepest Shortfalls in June-July-August (Australia’s mid-winter) look to be about the same in each of these years - but more on that later. This indicates that the quantity of reliable dispatchable generation still needed to keep the lights on has remained relatively unchanged, despite (for example) additions of battery storage capacity projects.

Year 2.1: 13 June 2025-17July 2026 on the NEM

For the rest of this post I’ll focus on the recent 1.1 years of data, otherwise there will just be too many plots.

First, in Figures 2, the ½-hourly power flows of the five NEM States are presented in descending order of Demand. Note: the vertical MW power scale is the same for each plot, giving an accurate visual representation of the relative sizes of the States’ electrical energy flows:
- NSW: Max 15,521; Min 4,339; Average 8,871
- Qld: Max 12,191; Min 3,563; Average 7,394
- Vic: Max 11,831; Min 3,260; Average 5,943
- SAus: Max 3,923; Min 580; Average 1,723
- Tas: Max 2,095; Min 702; Average 1,187

Figures 2: The NEM States, 13 June 2025 thru 17 July 2026:

NSW [top left, and Figures 4 below] very occasionally meets its Demand solely from its ‘renewable’ generation.
Both Qld and Vic [top centre and top right] are continuously in Shortfall throughout this period.
SAus [bottom left, and Figures 3 below] continues to balance its ±2 GW average capacity Solar-heavy grid by leaning heavily on its connected neighbours [its power Import and Exports are plotted along the bottom].
Tas [bottom right] is dominated by largely-dispatchable Hydro, which can most of the time be controlled so as to fully meet the State’s relatively miniscule ±1 GW average in-State Demand, and provide export power to connected States.

I’ve gathered data on battery charging / discharging only from 01 March 2026. This - because of the [expletive deleted] variability of numbers and positions of data columns in Open Electricity data files - requires manual validation each added file of data. [The process is a complete b@lls-ache, which is why I only went back as far as 01 March].

Year 2.1: South Australia (SAus), Details:

Figure 3A: SAus 13Jun2025 to 17Jul2026:

The numerical information in the table at the bottom of Figure 3A, e.g. Demand Max, MW 3,923 etc., is for the whole 1.1 year period 13Jun2025 to 17Jul2026.

Figure 3B: SAus 01Mar to 17Jul2026 - Curtailments and Exports:

Note: the vertical MW scale on the left-hand axis is the same as on the right-hand [RH] axis. The RH axis is simply displaced downwards so as to separate the plots for greater clarity. This also applies to Figures 3C, 3D and 3E, and Figures 5.. below.

Figure 3C: SAus 01Mar to 17Jul2026 - Battery Charging & Discharging:

The numerical information in the table at the bottom of Figure 3C, e.g. SAus Total In-State Demand: MWh since 01 Mar 2026 00h 5,414,724, etc. is, as it says, using only the latest 138 days ~20 weeks of data through the Autumn into Winter. By and large, the Shortfalls are greater at the end of this period (especially 21 June 2026 and later), but I see no clear signal that Batteries responded then to the greater need.

We do, however, see that over that ~20 weeks, the round-trip efficiency (RTE) of the fleet of SAus Battery Energy Storage Systems (BESS) was 78.5% - in other words, 46,685 MWh or a little over 20% of the electrical energy fed to the SAus BESS array was lost.

Figure 3D: SAus 17Jun to 17Jul2026 - Curtailments, Imports & Exports:

There seems to be some correlation in Figure 3D between Shortfalls and Curtailments, Imports & Exports. When Shortfalls are bumping along the zero axis (i.e. when in-State Demand was being met by [fossil-free] Supply), either or both Wind Curtailment and Exports are visible. When Shortfalls are large, Curtailments are barely visible and Imports are active.

All as you’d expect when you have to obey the laws of Physics and keep the grid in balance. But it’s a portent of things ultimately to come: when all the connected parts of the NEM are packed full of ‘renewable’ generation sources, the Solar always up and down nearly in lock step across the NEM, and sometimes with Wind lulls covering large areas of the NEM territory, see Figures 4 below.

Is ever more BESS1 the answer? Because at the moment it’s difficult to see any indication yet of BESS riding to the rescue in Figure 3E which features some low and very low Wind periods.

Figure 3E: SAus 17Jun to 17Jul2026 - Battery Charging & Discharging:

If we look again at Figure 1B we can see that there were NEM-wide lulls in Wind in June 2025 and again in June 2026. Zooming in on those periods and looking at combined Wind across the whole NEM and [fossil-free] Shortfalls, we get Figures 4:

Figure 4A: Combined NEM Wind, 14 Days in June 2025:

Every evening from 26 June 2025 for the next 8 days the worst Shortfalls were 26 GW to 24 GW - the measure of dispatchable power needed to keep the lights on at the times of most stress on the NEM.

Figure 4B: Combined NEM Wind, 14 Days in June 2026:

A year later the worst Shortfalls were 25 GW to 23 GW for 6 days from 21 June 2026 - again, a marginal improvement in the NEM grid, or luckier with the weather?

Year 2.1: New South Wales (NSW), Details:

Having looked at South Australia in detail, I’ll finish by taking a more detailed look at the State with the greatest Demand on the NEM, New South Wales.

Figure 5A: NSW 13Jun2025 to 17Jul2026:

Figure 5B: NSW 01Mar to 17Jul2026 - Curtailments:

The latest 138 days ~20 weeks of data for NSW shows distinct patterns of higher [Utility Solar] Curtailments when in-State [fossil-free] Shortfalls are lowest. Solar being in phase across the NEM, there is no outlet for that excess power.

Figure 5C: NSW 01Mar to 17Jul2026 - Batteries:

We see that over that ~20 weeks, the RTE of the fleet of NSW BESS was 82% - in other words, 96,538 MWh or about 18% of the [mainly fossil-generated] electrical energy fed to the NSW BESS array was lost.

And we see that currently the quantity of power received from discharge of batteries into the NSW grid is barely 2.3% of the Shortfall over this period.

It’s a difficult problem, this energy ‘transition’ lark.

Ah, but I think I see an answer.

Referring back to Figures 4A and 4B, there’s an obvious solution for the NEM to make its ‘decarbonisation’ much, much easier:

Ban the month of June!

Copyright © 2026 Chris S Bond

Disclaimer: Opinions expressed are solely my own.

This material is not peer-reviewed.

I am against #GroupThink.

Your feedback via polite factual comments / reasoned arguments welcome.

1

SAus Battery Energy Storage Systems (BESS) to 17Jul2026: the Open Electricity list of ‘operating’ BESSs in South Australia [screen-grab 17 July 2026]

Note that two of the biggest, Summerfield 1 and Summerfield 2, each has a dark blue dot and a light blue dot, and each location is listed as having 960 MWh of energy storage/ 240 MW of power capacity. However, as shown below [a combination of two screen-grabs, each obtained when you click on either name in the list], Open Electricity presents them as having a 480 MWh storage used for Charging, and a different 480 MWh storage used for Discharging… huh??

The UK National Energy System Operator (NESO) provides a data portal of “Historic generation mix and carbon intensity”.

The NESO data for ZERO_CARBON_perc [percentages] reported each ½-hour time interval throughout the datafile is wrong. Real ZERO_CARBON percentages are lower / much lower than those reported in NESO’s data-file.

The NESO GENERATION data for whole years is not reconciled to energy quantities reported in the Digest of UK Energy Statistics (DUKES) [National Statistics]. This means real percentages [of LOW_CARBON and RENEWABLE] are likely lower than reported in NESO’s data-file .

If NESO cannot get simple maths right, how are we meant to trust NESO claims?

Also, “All Net-Negative values are curtailed at zero” means NESO fails to report round-trip energy losses for Pumped Hydro and other forms [e.g. battery] of electrical energy storage: a significant and increasing misrepresentation.

NESO Data (available from 01 January 2009)

I’ve recently become aware of the UK National Energy System Operator (NESO) data portal of “Historic generation mix and carbon intensity”. The introductory blurb states:
“… It has seasonal decomposition applied to correct missing or irregular data points. The data is subject to change due to a data cleansing process taking place to provide the most accurate figures.
Batteries (NET discharge) are currently included in the OTHER category. Transmission-connected solar farms are currently included in the OTHER category. Pumped Storage units (NET) are represented in the STORAGE category.
All Net-Negative values are curtailed at zero.
Updates will be released later in 2026, to highlight BESS (Battery Energy Storage System) and Transmission Solar values.”
[I have modified paragraph breaks to make clear the various claims being made. Note also to NESO: today is 2nd July i.e. half-way through the year, where are the ‘updates’?]

Anyway, excellent! I thought. Here is data from the grid system operator which is being corrected and improved in near-real time…

The NESO comma-separated variable (.csv) data-file currently comprises nearly 307,000 rows = data sets, with data recorded every 30 minutes1. It is currently a reasonably-modest 59Mb. It can be readily converted to Excel which can then be used for number manipulations (SUM, AVERAGE, MIN, MAX, etc.) The same (or extrapolated) data can also be readily plotted. Double excellent!

I hoped this would save me from having to apply adjustment factors to the Gridwatch data I’ve used heretofore to force overall agreement between Gridwatch energy quantities and those in the National Statistics publication Digest of UK Energy Statistics (DUKES) produced by the Department for Energy Security & Net Zero (DESNZ), see Figure 1.

Figure 1: DUKES 6.2 for 2020 thru 2024:

Because when NESO claims: “… data is subject to change due to a data cleansing process taking place to provide the most accurate figures”, they surely mean they are rationalising their data to ensure agreement with the official energy statistics published in DUKES…

NOT AT ALL.

Details of how I analysed the NESO data are included in Appendix 1.

Figure 2: Whole Year 2020:

Clearly, NESO’s “data is subject to change … to provide the most accurate figures” does NOT extend to rationalising the year’s total MWh of GENERATION to that presented in UK Energy Statistics. The total MWh of GENERATION is the denominator in all the calculations of [ENERGY]_perc, so using NESO’s lower value of total MWh of GENERATION artificially inflates NESO’s reported [ENERGY]_perc values.

I found that the totals of Wind generation reported by NESO are quite similar to DUKES. The Solar totals are less similar, but NESO states that ‘Transmission-connected solar farms are currently included in the OTHER category’ leaving a degree of fuzziness / uncertainty in the NESO reporting of that / those parameter(s).

I’m not sure that I’ve correctly inferred the origin of the numbers in NESO’s derived columns entirely correctly, reference Appendix 1. Regardless, some of the numbers visible in the above snapshot are simply and literally incredible. For example, in my row 17570 (the data for 31 Dec ‘20 22:30):
NESO LOW_CARBON 15,443 MW is > NESO ZERO_CARBON 14,415 MW;
yet NESO LOW_CARBON_perc 48.5% is < NESO ZERO_CARBON_perc 53.6%

Etc. etc.

Make it make sense, NESO!

Figure 3: Whole Year 2021:

It is a similar story with 2021 [and subsequent years’] data. NESO’s figures for GENERATION are not reconciled to DUKES statistics, and NESO’s reported ZERO_CARBON generation total is NOT consistent with the input data. Consequently the percentages, particularly of ZERO_CARBON, reported by NESO in this data-file are markedly exaggerated. However, the Wind percentage total is quite close to the DUKES number, and Solar also may be.

Again, quick check of the ZERO_CARBON numbers from the top row of the above snapshot from whole year 2021:
LOW_CARBON 20,838 > ZERO_CARBON 18,875, but
LOW_CARBON_perc 73.4 < ZERO_CARBON_perc 82

Figure 4: Whole Year 2022:

Again, the relative sizes of the NESO ZERO_CARBON numbers and corresponding NESO ZERO_CARBON_perc values don’t make sense.

Figure 5: Whole Year 2023:

NESO ZERO_CARBON numbers again…

Figure 6: Whole Year 2024:

The total MWh of GENERATION from the NESO figures is much closer in whole year 2024 to the DUKES total. The Solar total is a match if “OTHER” is ignored: I don’t know if it should be.

However, look at those NESO ZERO_CARBON numbers yet again…

A Pattern?

This post has some similarity to the one I wrote in January of this year on the Australian National Energy Market as reported by Open Electricity. Different jurisdictions, different data sources, apparently similar issues of opaque number-crunching being done in the background that results in over-claiming progress with energy ‘transition’. How odd.

Am I Just Being Mean?

Poor NESO, you might be thinking. Couldn’t I have quietly sent an email to their contact details and given them the opportunity to make corrections without any egg on face?

Well, no. They are a well-funded quango2 responsible for keeping GB’s lights on. If they cannot do simple arithmetic, I think people should be aware of it.

After all, it begs the question: how else are they failing?

Appendix 1: Analysis of NESO “df_fuel_ckan.csv“ file

I searched for background technical information on the calculations behind the derived numbers in the file: I couldn’t find it on the NESO data portal home page.

The issue with NESO’s comma-separated values (.csv) file is that it cannot have e.g. explanatory or notes tabs, so the only information on what each variable is is in the column headings:
Columns A to M [data included for example set 2020-05-29T15:00:00 = row 200000]:
DATETIME text field format yyyy-mm-dd hh:mm:ss [= date time 29 May ‘20 15:00]
GAS 5091
COAL 0
NUCLEAR 4757
WIND 3058
WIND_EMB 1302
HYDRO 241
IMPORTS 4086
BIOMASS 2893
OTHER 122
SOLAR 6598
STORAGE 0
GENERATION 28148 [= sum of the listed generation quantities]:

Ignoring column N [CARBON_INTENSITY] as its derivation is secondary and opaque.

Columns O, P, Q and R [again with the data from 2020-05-29T15:00:00] are:
LOW_CARBON 18,849 = re-created by adding Nuclear + Wind + Wind Emb + Hydro + Biomass + Solar:

ZERO_CARBON 10,949: from the numbers listed the closest I can get to re-create this value is by adding Wind + Wind Emb + Solar = 10958 [not 10949, but close]:

RENEWABLE 11,199 = re-created by adding Wind + Wind Emb + Hydro + Solar:

FOSSIL 5,091: = GAS + COAL, ok

Then scrolling across to Columns AE, AF, AG and AH we find that NESO’s listed ZERO_CARBON_perc of 67.7% in Column AF is seriously in error. For the set of numbers from 2020-05-29T15:00:00 this should be 10,949 / 28148 i.e. 38.9%

I don’t know how you feel, but as soon as I find one derived number so seriously in error I begin to doubt the validity of the whole series.

Anyhow, having reconstructed how (I think) the derived values in NESO’s .csv tabulation are generated, I can analyse whole-year results and compare them with DUKES 6.2, see above.

Notes:

For the version of this data I’ve used for the screen-grabs above, I:
- focussed on recent years for which the generation capacities of our Wind and Solar fleets are high enough compared with future plans, that extrapolation is less of a stretch. Hence for this post I’m only looking at the NESO data from 01 Jan 2020 onwards, so I deleted all the rows before that date to reduce the size of the file;
- inserted columns next to the text date and time so as to convert each to plottable date and time [shown with pale green background in Column F].

Then I’ve used column summations in each of the energy columns to determine the whole-year quantities of energy generated by each technology, for example total GENERATION. The NESO data is recorded in MW in each 30-minute interval. Therefore the whole-year’s energy is the sum of the MW *30/60 to get MWh, then divided by 1000 to get GWh; as shown in the example below:

Using what I’ve inferred are the derivations of ‘LOW_CARBON’, ‘ZERO_CARBON’ and ‘RENEWABLE’ energies for a year I can then generate comparisons between column summations of NESO figures [T, U, V & W in the image below] versus the values [in row 17575 shaded pale blue] I can derive from the raw data:

LOW_CARBON is a close match; column summation 151,559 GWh versus 150,068 GWh derived by adding Nuclear + Wind + Wind Emb + Hydro + Biomass + Solar.
ZERO_CARBON is not a match at all; column summation 125,898 GWh versus 80,371 GWh derived by adding Wind + Wind Emb + Solar.
RENEWABLE is a close match; column summation 86,172 GWh versus 84,681 GWh derived by adding Wind + Wind Emb + Hydro + Solar.
FOSSIL is an exact match.

What of it? you may ask. Well, the NESO data includes those derived columns LOW_CARBON_perc; ZERO_CARBON_perc; and RENEWABLE_perc
If, particularly, the ZERO_CARBON numbers in each data set are not consistent with the basic energy data, then the ZERO_CARBON_perc[ent] figures in the NESO data-file are significantly misleading:

row 15573: GENERATION = 275,520 GWh; ZERO_CARBON = 125,898 GWh (NESO); ZERO_CARBON_perc = 45.7%
row 15575: GENERATION = 275,520 GWh; ZERO_CARBON = 80,371 GWh (CSB); ZERO_CARBON_perc = 29.2%

On top of that, if we base the comparison on the DUKES 6.2 (official UK statistics) total generation figure of 310,296 GWh in 2020, and ZERO_CARBON = 80,371 GWh which I can justify: the ZERO_CARBON_perc is lower still at 25.9%

Conspiracy or cock-up?
Lies, damned lies and statistics?
Take your pick!

Copyright © 2026 Chris S Bond

Disclaimer: Opinions expressed are solely my own.

This material is not peer-reviewed.

I am against #GroupThink.

Your feedback via polite factual comments / reasoned arguments welcome.

2

I searched “is NESO a quango?” and got this response:

We are in the midst of a heatwave, and this heatwave feels worse than the last one.

It’s been reported that solar farm output has been reduced because of the high temperatures, but I find it difficult to discern that signal in the Gridwatch data for the last week, see Figure 1.

Figure 1: UK Demand, Wind & Solar, 1d and 7d thru 2026-06-25 1500:

The really hot days in southern UK began on Tuesday (23rd June), when [looking at the right-hand charts] Solar peaked at about 14GW1. Wednesday was even hotter, yet again Solar reached 14GW. Today (Thursday) is about as hot as yesterday, and again the entire fleet of UK Solar was generating ~14GW at its peak. Very good, I’m sure our Energy Secretary is celebrating… except, not so fast, Mr Milliband!

Just look at the Demand charts at the left: Tuesday thru Thursday they are peaking at 40GW, with night-time minima at around 28GW. And because Wind has been consistently 5GW or below since the end of Friday last, the scale of the ‘transition’ remaining to do is traced by the red CCGT (gas) line in the middle charts. Once the sun sets, this levels out at around 15GW. What multiple of Wind would be needed those nights? Take, for example, Wednesday: Wind was ±3GW, hence future Wind would have to provide ~12/3 = 4 times current Wind generation to have a chance of keeping the lights on at night in this summer heatwave.

Of course, we already heavily rely on interconnectors to meet UK Demand a lot of the time, see the charts down the right hand side of Figure 2.

Figure 2: Gridwatch as of 2026-06-25 1500:

And because the ‘Wind is always blowing somewhere’™, we can always rely on our neighbours being willing and able to supply us with the power we need even as they progress through their own energy ‘transitions’, right?

Not if you look at energy data for the same week from our near-neighbours. Like I did some time ago for a wide-area lull that occurred November 2024, again using a selection of Energy Charts plots to illustrate the minimal Wind generation currently available across much of Europe.

Figure 3: the Euro Heatwave:

Figures 4: Demand, Residual Demand, Wind, & Solar; nearby countries:

Wind generation has been flattened across Europe… it’s almost as if the ‘intense record-breaking heatwave in the UK and Europe has been caused by a static and large area of high pressure’.

Doesn’t a static area of high pressure mean hardly any Wind, even when it gets dark? Very inconvenient!

Wouldn’t it be better for more people to have an energy strategy focussed on production of cheap reliable power? Then we could afford to run air conditioning when it gets this hot!

Copyright © 2026 Chris S Bond

Disclaimer: Opinions expressed are solely my own.

This material is not peer-reviewed.

I am against #GroupThink.

Your feedback via polite factual comments / reasoned arguments welcome.

This post is a follow-up to some posts last year which, between them, should provide you with all the context you might need: How’s it Going, Ed? through More Over-Abundant Wind to DESNZ to Include (some) Reality.

For this post I’ve downloaded GB power data from midnight at the beginning of 01 January 2025 through mid-Monday, 09 February 2026, from Gridwatch. (You will see I’ve annotated minor gaps in the data.)

I’ve processed this data using the ‘2025’ file I used for the ‘How’s it going, Ed?’ post linked above, i.e. continuing to use all the 2024 adjustment factors and multipliers as explained in my Great Britain Reality post.

The downloaded sets of data comprise GB energy flows recorded every 5 minutes i.e. 5/60 hour. I adjust the raw numbers to get closer agreement of total energy from each source with the most-recently-available official record (DUKES) - all as explained in the ‘G B Reality’ post.

Hence I can plot adjusted Demand versus adjusted Wind and adjusted Solar generation as shown in Figure 1.

Figures 1: 01 Jan 2025 thru 09 Feb 2026, Adjusted to ≈ DUKES:

You can see in Figures 1, GB is getting close to having sufficient ‘renewable’ energy on cooperative-weather days so as to reduce Shortfalls to ~ zero from time to time. Note we import up to nearly 11 GW at times via the interconnectors: but there is no guarantee that at a time of high UK need we would be allowed to import if neighbours were similarly strapped for power.

The National Energy System Operator (NESO) used to say explicitly on its website that it ensured
Generation = Demand *every* second of *every* day

… for example, like this:

Now, however, NESO blathers on about ‘holistic thinking’, while this simple statement of its key fundamental responsibility is gone. Worrying.

Anyway, let’s look in more detail at three areas of the charts in Figures 1 where we can see sustained deep dips in the Shortfall plot. Specifically, in January 2025 (see Figures 1A); in July-August 2025 (see Figures 1B); and in October 2025 (see Figures 1C).

Figures 1A: 01 thru 29 Jan 2025, Adjusted to ≈ DUKES:

Typically for the UK in winter, Demand was varying between 30,000 and 50,000 MW for quite a lot of January. Solar, also typically for us in winter, was pathetically minimal in the days, and zero every 16-hour night; and Wind went mostly AWOL for a couple of weeks.

For the energy storage afficionados, I would eye-ball that as an average -32,000 MW from midday 08 Jan thru midnight 23 Jan, i.e. for about 15 days = 360 hours. I’ve sketched that in purple on the bottom image in Figures 1A.

That’s about 32,000 x 360 = 11,520,000 MWh cumulative Shortfall. But that’s with current actual capacities1 of ‘renewable’ generation. We’ll see later in this post what effect NESO’s planned higher capacities of ‘renewable’ generation might have on this energy storage requirement.

Figures 1B: 10 July thru 07 Aug 2025, Adjusted to ≈ DUKES:

In July-August 2025 we obviously didn’t suffer a ‘dunkelflaute’ since it was too sunny in the day-times to be considered ‘dark’. But we certainly had an extended lull in the Wind. This while we also experienced lower than usual Solar generation in the long summer days. I’ve again sketched the result on the lower image in Figures 1B - Shortfall averaging ~19,000 MW for about 16 days = 384 hours.

Figures 1C: 02 thru 30 October 2025, Adjusted to ≈ DUKES:

Shorter autumn days, an extended lull in the Wind, and Demand beginning to ramp up as the weather cooled, resulted in another extended period of Shortfall in October. Roughly -28,000 MW by 12 days = 288 hours.

That’s about where we are. Holistically, or otherwise.

Into the Future

So, let’s see how this 400 days (110% of a year excluding the 3-day spell of missing data) of real weather-dependent power generation looks when we extrapolate to end-20302 via Wind and Solar (and Demand) multiples.

I make the gross assumption that, despite its dithering and general ineptitude, HMGov will by the end of 2030 still have the same largely CO2-free nuclear generation capacity as we have now.

So, for each 5-minute interval of Gridwatch power data, I multiply the adjusted power from Wind and from Solar by what I estimate are the relevant multipliers from NESO plans; I subtract that (W’ + S’) total from the slightly increased net Demand D’ for the interval (allowing for Imports / Exports and Nuclear to stay as-were) and thus find whether there would be:
- a [potential] Surplus if W’ + S’ > D’ - [potential] because Generation must = Demand;
- a [fossil-free] Shortfall if W’ + S’ ≤ D’
in every interval.

Gridwatch does not capture real-time constraints / curtailments for (usually, currently) grid capacity limitations reasons, but these increasing policy-failure3 costs are loaded on bill-payers, and as I indicate, they are destined to grow for ultimate physics-limitation reasons.

The results of the arithmetic extrapolations are shown in the plots in Figures 2.

Figures 2: 01 Jan 2025 thru 09 Feb 2026, Extrapolated to Dec 2030:

Note the extreme peaks of both Wind and Solar, and the rate of change of both, in the upper chart. All the sources of ‘firming’ would have to be able to ramp as fast to keep the lights on.

The lower chart shows the peak power Shortfall is -50,000 MW = -50 GW. That’s the total capacity of the ‘firming’ (likely from gas turbines) that would be needed to keep the lights on in the worst circumstances this period. The peak Shortfall occurred 22nd January 2025 at about 6pm when Solar was zilch.

Note also in the lower chart: the sheer number of times that ‘renewables’ cannot satisfy Demand, and that therefore something other than ‘renewables’ will need to step in, fill the gap, then step away again. If that’s aero-derivative gas turbines, ok, they’re made for surges of power. Other generation hardware like CCGTs, not so much.

Figures 2A: 01 thru 29Jan 2025, Extrapolated to Dec 2030:

Cumulatively, that Shortfall 09 Jan thru 23 Jan 2025 was, roughly-roughly, -22,000 MW for ~15 days = 360 hours, or roughly 7,920,000 MWh. Or, a bit less than -22,000 MW but from about the end of 03 Jan? You decide.

If that quantity of energy were to be supplied from energy storage rather than dispatchable fossil-fuelled generation, it’s A LOT:
Multiple Dinorwyg pumped hydro energy storage schemes at 1,728 MW / 9,100 MWh each? Yup, about 870 of those.
Or how many Thurrock Storage BESSs at 600 MWh each? Around 13,000? Yikes!

Never forgetting, of course, that energy storage is not the same as energy generation: you have to have ‘charged up’ your storage before you can discharge it. If it’s run flat - as is highly likely by the end of that extended period of Shortfall around 23 Jan - you’ll get nowt from it.

Figures 2B: 10 July thru 07Aug 2025, Extrapolated to Dec 2030:

Not as bad as in January, but almost every night there’s quite a substantial Shortfall, and around late 28 July thru mid-30th, about 48 hours of -20,000 MW... 960,000 MWh, or about 1,600 of those Thurrock Storage BESSs.

Figures 2C: 02 thru 30 October 2025, Extrapolated to Dec 2030:

Cumulatively, that Shortfall from late 07 Oct thru the end of 18 Oct 2025 was roughly -22,000 MW for ~11 days = 264 hours, or roughly 5,808,000 MWh.

You can see where I’m going with this, can’t you.

The chances of NESO / DNZ overseeing the building and connecting all of that infrastructure by the end of 2030?

The chances of them messing up energy security by dynamiting some dispatchable assets because the ‘Net Zero’ timetable says it must be done by such and such a date?

Or, from paying through the nose to make the ‘holistic vision’ urgently fit reality, the chances of chasing from our shores the last vestiges of our industry?

Fellow Brits, I’m worried. You?

Copyright © 2025 Chris S Bond

Disclaimer: Opinions expressed are solely my own.

This material is not peer-reviewed.

I am against #GroupThink.

Your feedback via polite factual comments / reasoned arguments welcome.

Background

This post is again on aspects of Australia's National Energy Market (the NEM) and its progress with its ‘decarbonisation’ [aka deindustrialisation] journey. It follows this 01 February 2026 post on LinkedIn in response to a 30 January 2026 article from The Guardian [link below].

At the time of writing the LinkedIn post has received many reactions, some highly approving: proof of #GroupThink in action.

(There are also more than 70 comments - two of which are from me, including reference to my post about the NEM exaggerating its percent ‘renewable’ claims.)

The Guardian article which this LinkedIn post featured so approvingly was headlined:

“Australia’s grid now relies on renewable energy as much as coal. Those who doubted it look foolish”

“Those who doubted it look foolish”? Really?

As is often the case -

The devil is in the Detail

The article’s focus was the previous week in January 2026 when high temperatures across parts of eastern Australia resulted in high power Demand, and how “solar provided 30% of all electricity in the country’s main grid, which supplies the five eastern states and the ACT. That’s across day and night.” [My bolding]

“… across day and night”. Really? Let’s have a look at what the data can tell us, if only we are willing to open our eyes (and minds) to see:

Figure 1: January 2026 in the NEM:

Later on in this post I explain how I derive the Demand1 (purple) as well as the [fossil-free] Shortfall (red) plots.

Engaging with reality, we can see that the difference between Demand and the total of low-carbon sources of power, varies between around -5,000 MW in the middle of summer days, and a yawning chasm of around -25,000 MW in the middle of hot nights, even when Wind is cooperating.

Follow the Guardian’s urging and Australia will be enjoying paleo power before too long.

The article also included this text:
“In parts of the year, renewables are now ahead. The Australian Energy Market Operator this week described the last three months of 2025 as a “landmark moment”, with renewables’ share in the quarter rising beyond 50% for the first time.”2

Instead of the hyperbole, let’s take a look at the ½-hourly data from the NEM for that 3-month period. As I did for Figure 1, I’ve plotted it in ways I doubt would ever be featured in the Guardian, nor Open Electricity for that matter. Doing so, I show there was never zero need for dirty dirty fossils to keep the lights on across the NEM grid in 4Q2025. The darned sun just kept going AWOL, regular as clockwork.

Unless you show (or at minimum, state) this obvious fact, I think your article will seriously mislead many readers.

I suggest, if you are at all interested in being factually transparent, you need a presentation such as included in Figure 1 or Figure 2. Much, much less misleading and more useful than that Guardian article / headline.

Figure 2: NEM ½-Hourly data 01 Oct 2025 thru end of 31 Dec 2025:

There is a fragment of truth in the article: averaged across the entire 3 months, ‘renewable’ sources of electricity (Wind plus both types of Solar plus Hydro plus tiny amounts of ‘Biomass’) satisfied just over 50% of the total MWh of 4Q2025 NEM electricity Demand.

But in NONE of those 2,208 hours, i.e. NEVER in any of those 4,416 ½-hourly intervals, did ‘renewable’ sources satisfy all of that ½-hour’s Demand. So, no way did it satisfy Demand “… across day and night.”

Of course, this relies on knowing what is Demand.

Apparently, for some it’s too hard to determine, while batteries are charging and discharging, and Wind is blowing and not blowing, and Solar power is up and down on the rigidly regular, and sometimes there are power Imports… Ah, no, that last item is only for a State, not for the NEM as a whole. (Nor for the isolated SWIS, but that’s an aside.) So Open Electricity doesn’t determine it. Hey, OE, these things called computers are really good at crunching numbers!

Because, actually no, it’s not at all hard to work out what Demand is. (At least close-enough for government work, as an old colleague used to say).

The fundamental principle of keeping a power grid stable is that:
Electricity Supply must = Demand every ½-hour. (It’s physics.)

Ergo, Demand must = Supply every ½-hour.

That is, for every ½-hour interval of NEM data, Demand equals the arithmetic sum of all the power flows. Negative power flows (into batteries, or pumping water up hills) just act as negatives in the summation.

So that’s how I can determine the Demand ½-hour by ½-hour throughout the period, which allows me to produce the purple Demand plot in Figure 1 and Figure 3.

Figure 3: NEM ½-Hourly Demand and Shortfalls, 4Q 2025:

For clarity, I omitted Hydro from Figure 3. (You can see from Figure 2 how relatively minor the hydro generation is, in context.) Instead I plotted Demand (purple), which is how I can plot the [fossil-free] Shortfall (red) i.e. by how much all the low-carbon sources of electricity failed to meet Demand each ½-hour.

And, in the Excel file, you can have a simple count of all the ½-hour intervals when Shortfall was ≤ 0. That’s 100% of the time, folks.

But… Batteries

Ah, yes, batteries to the rescue! Open Electricity has recently modified how it presents its Battery Energy Storage System (BESS) tracking to differentiate between operating and commissioning facilities.

(I wonder if my scathing comments in previous posts had anything to do with that? If yes, dear OE, please take on board my scathing comments herein about including Demand and [fossil-free] Shortfalls in your NEM and State-by-State presentations. Also, dear OE, please make granular data - ½-hourly at minimum - available for longer than just the last 7 days. And for crying out loud, stop varying the number of columns in each .csv data-file depending on use or non-use of a marginal source of power in a given time interval: a column which does not jump around but which has regions of zeroes among the numbers would be hugely preferable!)

Figure 4: Operating BESSs on the NEM as of 07 Feb 2026:

So now, after the change to how the data is presented, the Facilities, Batteries, Region NEM, Status ‘Operating’, sorted in descending order of Capacity, produces the image shown in Figure 4. Little colour indicators show whether a facility is ‘operating’ (green) or ‘commissioning’ (amber). The Waratah Super Battery is shown as ‘operating’ although we all know of its major transformer woes (1oo3 wrecked, 1oo3 too suspect to be actually operated was the last I saw) and if you click to bring up the facility info it’s going at barely 1% capacity factor.

In this presentation we’ve lost the claimed total MWh installed: my guess is approximately 2 hours average for the ‘operating’ 6,195 MW ≈ 12,000 MWh.

The NEM fleet of BESSs is currently charging and discharging depending on power cost ‘arbitrage’: buying low and selling high. Whether that’s an instance of ‘privatising profits, socialising costs’ I’ll leave to Australian bill-payers / tax-payers / voters to decide.

What is completely evident from Figure 1 and Figure 3, however, is that there is no ‘surplus renewable’ power going into batteries: it’s mostly fossil generation.

I’ve identified one problem facing the NEM: Solar power alone cannot keep the lights on. There is a 24-hour cycle of power abundance and power poverty. Putting aside the even harder problem of seasonal variation, how much BESS capacity would be needed simply to smooth that abundance / poverty cycle into steady continuous power? (IF you get the BESS energy storage capacity you can obviously then choose to release energy from it faster or slower to better adjust to the real Demand cycle.)

According to the OE Records page for Solar generation, the highest ever day of Solar generation in the NEM was 09 December 2025, yielding 222,329 MWh of energy (with mentions of peaks of 23,858 MW at 1:25pm and 23,836 MW 1:10pm).

Using ½-hourly data for that day I produced the plot shown in Figure 5.

Figure 5: Smoothing NEM Solar Power Using BESSs:

If you average 222,329 MWh across 24 hours you would get a steady 9,264 MW. This on a day when Demand varied between 19,447 MW at 03:30, to 33,860 MW at 15:30.

So that steady BESS power release would be between 47.6% of Demand in the middle of the night, to 27.4% of peak Demand in the early afternoon. Useful.

But at a total cost for BESSs of something around AUD 80 billion or so.

Mindblowing!

Copyright © 2026 Chris S Bond

Disclaimer: Opinions expressed are solely my own.

This material is not peer-reviewed.

I am against #GroupThink.

Your feedback via polite factual comments / reasoned arguments directly relevant to the material in this post, are welcome.

1

As a reality-check on my numbers, I downloaded the 1-year x daily NEM comma-separated variable (.csv) data-set ending 05 Feb 2026. These are daily numbers, so are useless for telling us whether the lights would stay on, but the daily energy totals are valid and hence so too are the annual totals:

fossil Sources: 124,417.4
low-C Sources: 83,994.7
pumps & Hydro: 11,048.7
batteries: -448.3 ==> avg. RTE 80.1%
Total Supply = Demand: 219,012.6
total low-C + Hydro: 95,043.5
low-C + Hydro % of Demand: 43.4%

Background

Australia's National Energy Market (the NEM) operates the electricity grid across Eastern Australia. I’ve posted before on Australia’s developing electrical energy landscape, for example here, if you need background.

Open Electricity is a publicly-accessible website offering data and graphics purporting to show how far Aus has progressed on its ‘decarbonisation’ [aka deindustrialisation] journey.

Under “Transparency & Accountability” on the ‘about’ page it says:
“Open Electricity is developed under the Open, Accessible, Auditable Data (OAAD) framework. OAAD was developed by The Superpower Institute to accelerate Australia’s climate energy transition.” [My bolding]
“Getting measurement right is a fundamental building block for transparent markets. The OAAD framework will ensure that critical climate and energy data is available to all, allowing industry, researchers and policy makers to better inform and improve their work.”

… and “Other Supporters” includes these guys:

Okay, Open Electricity is clearly pro ‘renewables’.
How about those other aims: transparency; data available to all, allowing better outcomes?
How might those aims be affected by inaccuracies in the numbers presented?

What? Inaccuracies? Read on.

The issue with the Open Electricity numbers presented for the separate States appears to be driven by how the website [opaquely] deals with Import and Export energy flows and how they relate to the tabulated “Contribution to demand” numbers in the tables shown to the right of the plots. The worst-case example over recent weeks has been Victoria, so I’ll focus the detail on that.

Figures 1: Victoria, 7 Days, 03Jan-10Jan 2026:

The 7-day view presented by Open Electricity for a State (upper image) includes the handy table on the right. At the lower right corner of that table is the stated “Contribution to demand” of 548 GWh of ‘Renewables’ which is presented as 51.0%. Impressive, if true.

But the huge [hidden] question is: what is the Demand across that 7 days of which
548 GWh of ‘Renewables’ is 51.0%?

Open Electricity doesn’t publish Demand numbers. I assume that they know that electricity Supply must = Demand every time interval (this data is ½-hourly). I have been working on the presumption that Demand within a State in a given interval equals the sum of all the energy flows they call “Sources” minus those they call “Loads”.

Except, that doesn’t produce numbers that match.

In the table at the right of the lower image I present the results of my calculations.
For each source of energy, a number of GWh of power is shown to provide a percentage “Contribution to Demand”.
Hence divide the GWh number by the percent and you see the GWh Demand they must have worked from.
Accuracy is higher for higher percentages, so the derived Demand from the highest percent contributor is true Demand: for these numbers that is 1,276 GWh.

Then 548 GWh of ‘Renewables’ divided by 1,276 GWh gives 42.9% not 51.0%

Double-checking the numbers in the table, ‘renewable’ Sources do add up to 548 GWh.

Back-calculating Demand from 548 GWh of ‘Renewables’ equating to 51.0% would be 1,075 GWh which is incompatible with all the other entries in the table.

I note that the “Net” figure at the lower left corner of the table is 1,301 GWh, which I can arrive at by ADDING the Loads to the total of the Sources. But it is not obvious how or even whether Open Electricity is using that Net number - and it is certainly NOT equal to Demand.

Looking at the next week, again from Victoria, and it’s worse.

Figures 2: Victoria, 2 Weeks, 10Jan-17Jan 2026:

Similar story again.
Claim: 581 GWh of ‘renewables’ = 62.6%. V impressive, Victoria! I bet it makes you proud!

Except.
Demand back-calculated from 448 GWh of Coal (brown) being 37.9% = 1,182 GWh.
581 GWh of ‘renewables’ in 1,182 GWh = 49.2%
That’s over 13 percentage points lower than presented.

Fake news?

As this post has taken most of a week to compile, I’ve looked at the next week’s data. Similar exaggerated claims are evident for the worst State, which is again Victoria:

Figures 3: Victoria, 2 Weeks, 17Jan-24Jan 2026:

The % ‘renewables’ claimed for the other States all err similarly, i.e. claim is greater than reality, but not quite as dramatically. I’ll just summarise my results in Figures 4. [I generated all2 the detailed results, I just don’t wish to be tediously repetitive.]

Figures 4: NSW, S.Aus, Qld, NEM results Summaries, 03Jan-24Jan 2026:

The good news for Open Electricity is that for the NEM area, the actual percent ‘renewables’ looks to be slightly higher than claimed.

The less-good news is that the percent ‘renewables’ for each of the States look to be exaggerated by significant factors.

Where are those ‘Error Tracking Software’ guys when you need them?

Copyright © 2026 Chris S Bond

Disclaimer: Opinions expressed are solely my own.

This material is not peer-reviewed.

I am against #GroupThink.

Your feedback via polite factual comments / reasoned arguments directly relevant to the material in this post, are welcome.

2

Tas data is simpler as illustrated by the week’s data below:

There, imports provided 15.8% contribution to Demand, and ‘renewables’ was claimed to be 100 - 15.8 = 84.2 %. That’s a slightly low claim because of the varying proportion of ‘renewables’ in the imported power.

Congratulations, Australia & the NEM!

A new Solar generation record

[The link is in the sub-heading]

California is blessed with plentiful solar energy. Its main electrical grid’s Independent System Operator (CAISO) offers highly-fragmented views on its progress to ‘decarbonise’ CA electrical energy. This includes its burgeoning use of battery energy storage systems (BESSs). I’ve posted before, examples here and here, if you need background on CAISO.

It also publishes monthly ‘key statistics’ on how the whole ‘net zero’ effort is going in the Golden State. The latest report is the one for October 2025 dated 11/14/2025, from which I’ve copied three graphics to include in this post.

First, CAISO’s claimed MW of ‘Installed renewable resources’, per Figure A. I’ve added the annotations.

Figure A: CAISO Installed ‘Renewable’ Resources (October 2025):

When I report them in my posts, I put asterisks around *capacities*1 of weather-dependent technologies: I wish others would similarly flag the unreality of claims such as CAISO’s above.

Also in the October 2025 ‘key statistics’ report we see that two Solar peak MW power generation flows occurred in late July 2025; and we see the reported Wind and Solar Curtailments month by month: as in Figure B.

Figure B: Other CAISO Key Performance Statistics (October 2025):

They didn’t do the sums for you in that chart on the right [maybe embarrassment?] so I did: Wind and Solar Curtailments to date this year add up to 3,706,977 MWh.

Also note, Australia’s NEM / Open Electricity: the highlighted text in the right hand image states CAISO doesn’t count BESSs until they’ve ‘achieved commercial operation’. Cough, Waratah, cough.

If you look back to January’s ‘key statistics’ report it includes: ‘installed battery capacity’ = 11,454 MW [as of 1/31/25]. So in the nine months since there’s been an impressive 30% increase [14,904 MW / 11,454 MW].

Let’s see how all that battery capacity is being used across the CAISO region.

For reasons I outlined in the first paragraph of my ‘California Battery Reality’ post, getting usable data from CAISO is like extracting blood from a stone. Thus for this post I chose to download sets of data solely for ‘total batteries’ for seven consecutive days’ at the ends of each month. Seven days because it’s a complete week including weekday to weekend variations. The only exception to this was July, when I retrieved nine consecutive days’ data for ‘total batteries’ and for ‘hybrid batteries’, to ensure I captured those record-breaking Solar days.

Figures 1: Total Batteries: Last Week in January and in February 2025:

In the last week of January 2025:
- average total battery discharging was 23,178 MWh;
- average total battery charging was 26,660 MWh;
- giving an apparent round trip efficiency (RTE) of 87% that week;
- maximum discharge rate [to the grid] was about 5,200 MW.

And in the last week of February 2025:
- average total battery discharging was 31,333 MWh;
- average total battery charging was 34,921 MWh;
- giving an apparent RTE of 90% that week;
- maximum discharge rate [to the grid] was about 6,400 MW.

Both sets of plots are very similar in shape. Small quantities of overnight charging give way to large quantities of pre-dawn discharging; then all the batteries charge like heck during sunlight hours; then around dusk they all switch to discharging once more.

Figures 2: Total Batteries: Last Week in March and in April 2025:

In the last week of March 2025:
- average total battery discharging was 32,321 MWh;
- average total battery charging was 36,633 MWh;
- giving an apparent RTE of 88% that week;
- maximum discharge rate [to the grid] was about 7,200 MW.

And in the last week of April 2025:
- average total battery discharging was 33,829 MWh;
- average total battery charging was 37,283 MWh;
- giving an apparent RTE of 91% that week;
- maximum discharge rate [to the grid] was about 8,400 MW.

Both sets of plots are very similar in shape again. Smaller quantities of overnight charging give way to large quantities of pre-dawn discharging; all batteries charge like heck during sunlight hours; around dusk they all switch to discharging.

Figures 3: Total Batteries: Last Week in May and in June 2025:

To avoid getting repetitive, I’ll leave you to read the figures from the charts [click to zoom in if you’re in Substack].
RTEs are similar; average daily energy quantities discharged to the grid inch up to 33,229 MWh and 36,650 MWh respectively; in June the maximum rate of discharge to the grid broke through 10,000 MW.

Figures 4: Total Batteries, Demand and Solar: Last Week in July 2025:

For the record-breaking period at the end of July 2025 I’ve included the Demand and Solar charts to provide extra context to what the batteries were doing.

Daily average battery discharge to the grid was 38,611 MWh compared with daily average Demand of 620,372 MWh - i.e. 6.2% of Demand on average.

Daily average Solar was 226,700 MWh - i.e. 36.5% of Demand on average.

In the 5-minute-interval data, the maximum Solar power I found was 21,749 MW. This is a very close match to the claimed record of 21,774 MW at 11:56 a.m. i.e. one minute after my data-set. This also confirms to me that CAISO’s claimed Solar record doesn’t include Hybrid Solar (see below). I wonder why not.

Maximum battery discharge rate to the grid in this interval was nearly 10,800 MW.

Just to make sure I wasn’t missing something significant, and also to test my theory that Hybrid Solar was in some way ‘special’ for the purposes of CAISO data-gathering, I downloaded sets of Hybrid battery and Hybrid Solar2 data for those same 9 days at the end of July. I plotted these in Figures 5 [which - note - have *very* different vertical scales to the other plots].

Figures 5: Hybrid Batteries and Hybrid Solar: Last 9d in July 2025:

Hybrids are about 10% of the magnitudes of non-hybrids. If CAISO had added the maximum Hybrid Solar to non-hybrid Solar they could have claimed a record Solar generation around 2,200 MW higher than they did. Weird.

Figures 6: Total Batteries: Last Week in August and in September 2025:

For August and September, RTEs are similar again; average daily energy discharged to the grid are similar to, but slightly down on, those of July; in August the maximum rate of discharge to the grid broke through 11,000 MW.

Figures 7: Total Batteries: Last Week in October and in November 2025:

For October and November, RTEs are similar again; average daily energy discharged to the grid in October was 41,632 MWh i.e. higher than in July - an indication of the addition of a big BESS, perhaps? In both these months, however, the maximum rate of discharge to the grid was back below 9,000 MW.

How far do you think CAISO is from being powered solely by Solar energy, might you think? Nearly there? Well, by extrapolating from this data, you find: not quite. By a long, expensive distance, in fact.

Taking the day of peak [non-Hybrid plus Hybrid] Solar = 30th July 2025, it’s possible to establish how much energy storage MWh would be needed to smooth the Solar surge evenly across the whole 24 hours. [Of course you’re unlikely to want to release the stored energy back to the grid evenly; but once you’ve got sufficient energy storage, then you can regulate its release to the grid to match the actual Demand curve. But this simulation gives an indication of the magnitude of the MWh required to cope with *current* Solar energy.]

Figure 8: July 30 2025 Battery Simulation:

I’ve used 87% RTE in the simulation as that seems to be about the round-trip efficiency CAISO’s current fleet of BESSs are achieving.
I set the initial state of charge (SoC) of the BESSs to 98,000 MWh so as to keep the minimum SoC during the day to ≥ 10% to avoid damaging battery life.
Then 1.1 times maximum SoC (avoiding charging to ≥ 90% to avoid damaging battery life) comes to just over 153,000 MWh of electrical energy storage required.
Which is 3.7 times the current demonstrated MWh of BESS capacity;
or 52 times the capacity of the pre-fire Moss Landing BESS [the opening image via that link shows the turbine hall which was the seat of the catastrophic fire].
All this for a constant 10,547 MW of power across the whole 24 hours [but more realistically, with the day’s Solar released according to the Demand curve].

To put this into context, you can see in Figures 4 that Demand that day varied between ~23,000 MW and ~33,000 MW. The daily average Demand across those 9 days at the end of July 2025 was 620,372 MWh, i.e. around 25,850 MWh per hour every hour.

Conclusions

The CAISO fleet of batteries has recently demonstrated:
- energy storage capacity of at least 41,632 MWh in ‘total batteries’, plus probably another ~3,800 MWh in ‘Hybrid batteries’
- energy discharge power capability of at least 11,000 MW plus ~2,200 MW respectively

The entire fleet of Solar generation sources has demonstrated output of 253,117 MWh at up to 21,774 MW.

In order to ‘smooth’ current Solar generation across 24 hours using just battery energy storage systems, a total BESS capacity of just over 153,000 MWh would be required. This is ~3.7 times the current demonstrated MWh of BESS capacity.

Copyright © 2025 Chris S Bond

Disclaimer: Opinions expressed are solely my own.

This material is not peer-reviewed.

I am against #GroupThink.

Your feedback via polite factual comments / reasoned arguments directly relevant to the material in this post, are welcome.

Australia's National Energy Market (the NEM) operates the electricity grid across Eastern Australia. I’ve posted before on Australia’s developing electrical energy landscape, examples here and here, if you need background.

The Open Electricity website includes (under the ‘Facilities’ menu option) tracking of power facilities, including Battery Energy Storage Systems (BESSs), see Figure A.

Figure A: Open Electricity Count and Capacity of ‘Operating’ BESSs:

I was originally going to focus in this post on the non-operational BESSs from that list (which includes the biggest of them following news of a major transformer failure at Waratah.)

Ok, the Waratah Super Battery itself has not failed. But the Battery Energy Storage *System* (emphasis on that final word) can’t work without its three major 350kV transformers. One of which has failed catastrophically according to this separate report. Which has held back final commissioning of the whole “Waratah Super Battery” while inspections are performed on the remaining two very large, long-lead-time transformers.

But Waratah has not been removed from the NEM list - even temporarily - which raises the question: when is an “Operating” BESS actually operating? The NEM seems so eager to show an *impression* of progress, that it doesn’t wait for completion of commissioning before including a BESS on its list.

This begs the question: doesn’t a Battery Energy Storage *System* have to pass an electrical facility insurance requirement equivalent to the ‘72-hours performance test’ - standard for new petrochemical, refinery, etc. process units - before they can be included on the ‘operational’ insurance program?

If not, why not? And if they do, surely *that* should be the requirement before they can qualify for inclusion on NEM’s list… no?

Anyway, you can see for yourself by clicking on any BESS in the Open Electricity list whether it has been storing or discharging power. And a lot of them have not, or if they have, very little relative to their rated MW.

But then I realised that, ultimately, they’ll fix / replace failed transformers, install missing transformers, and otherwise get those BESSs up and running. And almost certainly install more and more.

Despite some different problems emerging, as indicated in Figure B:

Figure B: BESS Charging vs. AEMO Directions:

Who could predict that the grid operator might direct the operation of assets on the grid to support the grid? Except, aren’t those privately-owned assets? Ah, they’ll find a work-around, enough money is talking to make sure of that.

Anyway, let’s see how things are shaping up across the NEM, going State by State in descending order of average Demand.

Figures 1: NSW 13 June 2024 thru 20 Nov 2025:

Figures 2: Qld 13 June 2024 thru 20 Nov 2025:

Figures 3: Vic 13 June 2024 thru 20 Nov 2025:

Figures 4: S.Aus 13 June 2024 thru 20 Nov 2025:

Figures 5: Tas 13 June 2024 thru 20 Nov 2025:

Figures 6: Whole NEM 7d Snapshot, & 13 June 2024 thru 20 Nov 2025:

The [fossil-free] Shortfalls charts indicate how far (a long, long way) Australia is from powering itself using only ‘renewable’ sources of generation.

So that’s where Australia’s NEM region is, power generation-wise, presently.

Using this real ½-hourly data from across the vast NEM region we can extrapolate to get an indication of possible end-points or destinations assuming the continued use of ever more *capacities*1 of currently-available technology. I am using the same methodology as outlined in my previous Aus NEM posts, but now I have ~12,620 hours of ½-hourly data…

Never forgetting that Electricity Supply must equal Demand 60/24/365.

Base Assumptions

I will assume:
- the ‘transition’ will take place over the next ~20 years, i.e. will be complete by 2044
- the Aussie population will increase, and electrification will proceed, and Aussies won’t vote to become poorer in energy terms: hence NEM power Demand will increase by a factor 1.5 over this timescale
- [precipitation-dependent] hydro generation will provide around 13.5 TWh/y - same as currently
- all necessary grid expansions & increases in infrastructure capacity are simultaneously achieved over the same two decades.

Then, rather than pursue a somewhat arbitrary ‘net zero’ target, I’ll use a few scenarios to illustrate some possibilities for the NEM region in Figures 7 and onwards.

I’m looking for a practicable collection of generation technologies, each allowed sufficient share of the generation ‘pie’ i.e. income from supplying electricity, that none of them ultimately would need subsidies or favoured treatment.

Using this ~1½ years of real data I demonstrate that any credible multiples of Wind plus Solar plus energy storage are insufficient at times to keep the lights on. Therefore, flexible dispatchable gas-fired and/or coal-fired generation will continue to be required to provide energy security. Where an ageing generator needs to be replaced anyway, the extreme variability of the charts indicates the replacements will need to be able to ramp quickly and frequently.

Figure 7: Low LDES Capacity, & Low Wind and Solar Multipliers:

In Figure 7 I have assumed ‘low’ multiplication factors for Wind and for [Total] Solar, and a ‘low’ capacity of long-duration energy storage (LDES) equivalent to 18 times the Waratah Super Battery [Waratah] or three times the NEM’s claimed 13,799 MWh current total ‘Operating’ BESS. Except the maximum *power* to be stored in LDES is equivalent to 28 times Waratah’s rated power capacity, i.e. the power capacity requirement would set the distributed BESS requirement.

[For fans of pumped hydro energy storage, this power capacity requirement for energy storage would require more than ten Snowy 2.0s. Almost certainly the more cost-effective solution would be more and more BESSs.]

In Figure 7 I show there is insufficient generation to keep the lights on for nearly 60% of the ½-hour intervals. Consequently, dispatchable generation sources would be up and down like yoyos (more stress, more maintenance, more costs). Cumulatively, those [almost certainly] fossil-fired generators would need to provide 87 TWh/y i.e. around 40% of Demand. They would thus probably receive adequate income to pay for their construction and operation despite the added operational stresses and costs.

At the same time, on most days the Solar surge would be sufficient to fill the LDES requiring ‘surplus’ to be curtailed, but at least the LDES would be charged and discharged frequently-enough to provide adequate income.

In this scenario, Curtailment sums to around 38 TWh/y, providing plenty of potential surplus electrical energy to produce new stuff - ‘green’ hydrogen / ammonia / cement / steel / whatever… Providing the issues of intermittency of ‘green’ power supply plus of complexity and costs can be solved.

Under a similar scenario, we could dramatically reduce that Curtailment TWh/y by installing 4 times that LDES capacity. That would at the same time fix the issue of too much power flow into energy storage needed at peak times:

Figure 8: Medium LDES Capacity, & Low Wind and Solar Multipliers:

In Figure 8 I have again assumed ‘low’ multiplication factors for Wind and for [Total] Solar, and a ‘medium’ capacity of long-duration energy storage (LDES) equivalent to 71 times the Waratah Super Battery [Waratah] or about twelve times the NEM’s claimed 13,799 MWh current total ‘Operating’ BESS. The maximum *power* to be stored in LDES is accommodated by this configuration. Minor issue [sarc] is that this is at four times the investment cost for LDES.

Unfortunately under this scenario, there is still insufficient generation to keep the lights on for around 45% of the hours. Dispatchable generation sources would still be up and down like yoyos (more stress, more maintenance, more costs) and would need to provide 68 TWh/y i.e. around 30% of Demand. Likely sufficient income, but less than in Figure 7’s scenario.

The Solar surge would still be sufficient to fill the LDES on many days, requiring Curtailment of around 14 TWh/y unless extremely flexible additional Demand appears.

Figure 9: High LDES Capacity, & Low Wind and Solar Multipliers:

Comments on Figure 9 are along the same lines as the comments on Figure 8. Double the energy storage capacity and cost of LDES buys relatively little advantage. It looks like that scenario is far from optimal.

Hence for the next scenario I revert to ‘medium’ LDES capacity and, for illustration, double the multiplier on [Total] Solar.

Figure 10: Medium LDES Capacity, Low Wind and High Solar Multipliers:

The capacity of long-duration energy storage (LDES) is back to the equivalent of 71 times the Waratah Super Battery [Waratah], but the maximum *power* to be stored in LDES requires 90 times Waratah’s power rating.

The enormous daily Solar surges peak at well over 120,000 MW (120 GW), but there remain [fossil-free] Shortfalls [the red chart] almost every night. These add up to 35.6% of the ½-hour intervals / 23.4% of the Demand / 52.5 TWh/y required from dispatchable [fossil-fuelled] generators.

At the same time, the total Curtailment to maintain grid stability [Generation = Demand 60/24/365, remember] totals 152 TWh/y.

It looks like that scenario is also far from optimal.

Hence for the next scenario I stay with ‘medium’ LDES capacity, reset the multiplier on [Total] Solar back to ‘low’, and instead double the multiplier on Wind.

Figure 11: Medium LDES Capacity, High Wind and Low Solar Multipliers:

The daily Solar surges peak at around 75,000 MW (75 GW), Wind peaks at around 65,000 MW (65 GW), and still there remain [fossil-free] Shortfalls [the red chart] many nights in the winter seasons. These add up to 16.5% of the ½-hour intervals / 9.2% of the Demand / 20.6 TWh/y required from dispatchable [fossil-fuelled] generators.

At the same time, the total Curtailment required to maintain grid stability totals 77 TWh/y unless additional, new, very flexible Demand can be added to make use of it.

But as a possible solution to Australia’s electrical energy trilemma (energy security, environmental sustainability, and energy affordability), that looks more practicable. Especially with a proportion of the coal fleet ageing and hence needing to be replaced anyway.

However, the Figure 11 scenario leaves the LDES fully charged or fully discharged and therefore not earning revenue for periods of days or sometimes weeks at a time. See the detailed views in Figures 12.

Figures 12: 1st 3 Months / Mid 3 Months / End 3 Months of Figure 11:

Hmmm. It brings to mind that wise saying from Thomas Sowell:

“There are no solutions, only trade-offs.”

P.S. Cost Spikes for NSW BESS Charging (Modo, 26Nov2025):

… costing up to 20% of the entire month’s revenues? Ouch! That’s gotta hurt!

P.P.S. Carbon Capture and Sequestration (CCS) (LI 24Nov2025):

Gorgon CCS performance detail here.

Dratted Reality Keeps Spoiling our Perfect Plans

Copyright © 2025 Chris S Bond

Disclaimer: Opinions expressed are solely my own.

This material is not peer-reviewed.

I am against #GroupThink.

Your feedback via polite factual comments / reasoned arguments directly relevant to the material in this post, are welcome.

Kathryn Porter summarises the issues that show, if our policy-makers don’t change their energy priorities fast, the UK will end in a dire situation over the next few years.

How do we keep the lights on with 12 GW net firm capacity at risk of retirement by 2030? Speech to the Institution of Power Engineers, 13 November 2025

The Government’s new estimates slashed the predicted “load factor” – the proportion of the year turbines are expected to generate power – from 61pc to 43.6pc for offshore wind. The estimated load factor for onshore turbines was also revised down, from 48.7pc to 33.4pc.

But, hang on. As long ago as Dec 23, 2022 in Note 2 of my post “Three Years’ Data and Still Not Workable”, I was highlighting the actual measured load factors as reported in the official Digest of UK Energy Statistics 6.3 [xslx]:

I put wind and solar PV *capacity* within asterisks to draw attention to the fact that the design limit of the facility is not the output you can expect from it...
Across the whole of the UK fleet of wind and solar PV, DUKES 6.3 Load factors for renewable electricity generation [xlsx] over the last five years are as shown in the table below, with the definition of “Load factor” given in the note below the table. I have added the 5-year averages column...

If you clicked on that DUKES 6.3 link today (in late 2025), you would see something confusing. My captured numbers in the graphic above for years 2020 and 2021 are different from the numbers in the July 2024 version of the “DUKES_6.3.xlsx” file. I *think* this is because, from 2020 onwards, DUKES 6.3 began reporting load factors on two different bases:

[note 1] “Percentage of how much was generated compared to maximum possible generation - based on the average of capacity at the start of the year and capacity at the end of the year. See methodology note for more details.”

or

[Note 2] “Percentage of how much was generated compared to maximum possible generation - based on the generation and capacity of plants that were operational throughout the year. See methodology note for more details.”

When I last investigated the methodology note it left me none the wiser.

Which official UK energy statistics are (more) correct?

Goodness only knows, because DUKES 6.3 gives no hint or guidance.

But here are all the numbers from the July 2025 release (I have added the 5-year average calculations in the right-hand column):

DUKES 6.3 [July 2024 version] Load Factors Last Five Years:

I didn’t bother generating standard deviations: I think the variability in the numbers is sufficiently obvious. I also think it’s obvious that, if the quoted numbers in that Torygraph article are valid, 43.6pc for offshore Wind and 33.4pc for onshore Wind are still wildly optimistic.

In July 2025 DNZ published its
“Wind load factor methodology note
DESNZ SICE1 Methodology to Estimate Net Load Factors for Renewable Wind Technologies” [pdf] with Contents and Introduction as shown in Figure 1
[my highlighting, obvs]:

Figure 1: Reality Dawning:

Better a late nod to reality than never, but more is needed.

DESNZ, apply your trained minds to the Solar load factor which was fossilised with a value 0.17 by ancient legislation. Looking at the DUKES 6.3 data above it is consistently recorded at around 0.10 (10% ± ~1% ). Whereas…

Here is Note 6 from DUKES 6.2:

And last but not least, DESNZ, you need to include sensible design margins.

#KeepTheLightsOn

Copyright © 2025 Chris S Bond

Disclaimer: Opinions expressed are solely my own.

This material is not peer-reviewed.

I am against #GroupThink.

Your feedback via polite factual comments / reasoned arguments welcome.

See One Year in Australia's NEM and my Eastern Australia Progress posts for background, including on Australia's National Energy Market (the NEM) which operates the grid across Eastern Australia. I’ve observed and remarked on evidence of curtailment of ‘Utility Solar’, but it is good to be able to download data to show the quantities of energy being switched off.

But first, a catch-up to show the general picture as to how ‘decarbonised’ Aus power generation is getting now I’ve collected 16 months’ of ½-hourly data: see Figures 1.

Figures 1: Real Power Flows, Five NEM States, 16 Months thru 15Oct’25:

In Figures 1, for each State I have plotted:
- the calculated in-State Demand (purple);
- recorded Solar (Rooftop plus Utility) (orange/yellow);
- recorded Wind (green);
- recorded Hydro (blue); and
- the calculated [fossil-free] Shortfall (red).
The vertical scale is the same for all: maximum 16,000 MW [set by NSW]; minimum -12,000 MW [to capture the worst-case in-State Shortfalls].
Plotting all States on the same scale clearly shows the relatively small magnitudes of South Australia’s and Tasmania’s power systems in the context of the whole NEM.

On the South Australia plot in Figures 1 I also included [repeat of] Demand MW, Import MW and Export MW, all plotted against the right hand axis so I can clearly separate the charts. The demonstrated peak Import and peak Export capacities are both around 800 MW as compared with the average S.Aus Demand of 1,711 MW. Here is the simple explanation as to how S.Aus can ‘lead the way’ with its ‘renewable’ generation without unbalancing its grid: it has a nearly ±50% buffer against being under-supplied during low-Wind nights, or against being over-supplied when the weather gods smile on it during the days.

However, since 03 September 2025, Open Electricity ½-hourly data-sets include Wind Curtailment (MW) and Solar Utility Curtailment (MW) numbers.1 So we can now explicitly see when over-supply causes Curtailment in South Australia, as shown in Figure 2.

Figure 2: South Australia Curtailments in the last month:

In Figure 2, for S.Aus over the last ~month (15 Sep to 15 Oct 2025), I’ve plotted:
- the same parameters as in Figures 1, plus
- Curtailed Wind (mid-green, RH axis); and
- Curtailed Utility Solar (pink, RH axis).
I’ve magnified the vertical scale slightly to make the plots more distinct, but have the same total range (12,000 MW) on both left and right axes.

There seems to be some correlation between intervals of low or absent Shortfalls, and intervals of higher Curtailment. This possibly indicates lack of Export capacity, but it might also indicate local grid constraints, or a mixture of both effects.

Figure 3: New South Wales Curtailments in the last month:

Similar observations for NSW as for S. Aus. Maximum Utility Solar Curtailment was 2,835 MW - I guess we’ll have to wait to see if this is yet having the effect of disincentivising Utility Solar investors.

Figure 4: Victoria Curtailments in the last month:

Similar observations again. Maximum Wind Curtailment was 3,808 MW - disincentivising Wind investors? Pi$$ing off bill- and tax-payers yet? I guess we’ll have to watch the headlines.

Figure 5: Queensland Curtailments in the last month:

Because the Shortfalls are continuously strongly negative, I surmise that Qld Curtailments are driven by lack of local grid capacity.

Figure 6: Tasmania Curtailments in the last month:

I had to dramatically adjust the [right hand] scale for Tasmania Curtailments because they’ve been so minimal. One might suspect that’s because Tas can control its Hydro according to local need plus Export demand.

It’s almost as if Hydro is a different kind of ‘renewable’ generation, isn’t it.

Copyright © 2025 Chris S Bond

Disclaimer: Opinions expressed are solely my own.

This material is not peer-reviewed.

I am against #GroupThink.

Your feedback via polite factual comments / reasoned arguments directly relevant to the material in this post, are welcome.

A post on LinkedIn a few weeks ago featured a snapshot of Texas power generators as of 4:39 pm on Monday 21st July 2025 (Figure 0A). This prompted me to revisit Electric Reliability Council of Texas (ERCOT) data - via the EIA - to see how things are going.

Figure 0A: Texas Grid Snapshot 21 July 2025 16:39 CT:

It’s a shame most of the plot in Figure 0A is obscured, but anyway you can’t conclude anything useful from a snapshot. Instead, you need a run of data covering months (at least), and at good-enough resolution that you can see what’s happening at nights; and when the wind drops, and how long it stays low; and so on.

Because the iron rule of electricity grids is:

Supply MUST equal Demand… every minute of every hour of every day

But TEX is Getting More Batteries

According to Yes Energy, there is a huge pipeline of battery projects on the way, see Figure 0B. Also according to them, as of 29 April 2025, there’s just under 10 GW of battery energy storage operating.

Figure 0B: ‘Yes Energy’ on Texas Battery Pipeline 29 April 2025:

Ok, Texas’s future is battery-assisted1.

I’ll assume that the duration of batteries installed to date is on average 2 hours, so current electricity storage capacity available across TEX is ~20 GWh i.e. ~20,000 MWh.

TEX is one of two major US regions - the other is CAL, California - which has gone further than most in ‘decarbonising’ its power grid. However, unlike CAL, the TEX region has very limited interconnection capacity to neighbouring grids.

I’ve collected over 7,400 hours (~10.2 months) of continuous hourly data beginning 00:00 on Oct 23, 2024 through to very recent complete data available from the EIA.

[I chose to start on Oct 23, 2024 because that’s when the EIA began collecting data on ERCOT battery charging separate from discharging. (See also my post on Battery Reality.) For this post I once again use data for the TEX region from the US Energy Information Administration (EIA).]

Figure 1: TEX Main Hourly Data (Excluding Fossils)- since Oct 23, 2024:

The purple plot shows Demand; red shows Nuclear; yellow shows Solar (with / without batteries); and green is the plot of Wind (with / without batteries).

I’ve omitted Gas and Coal generation plots to avoid cluttering the plot, and to keep the focus on the current fossil-free sources of power generation.

We know that low Demand occurs each night, which we know is when Solar generation falls to zero. We can see the current large gap between maximum Wind and minimum Demand. So we can intuit that currently TEX power generation is far from being ‘carbon-free’.

The tabulation below the plot in Figure 1 shows the minimum, maximum, arithmetic average, and total MWh, of each of the existing sources of low-carbon power supply on the TEX grid.

[I haven’t investigated whether TEX interchange is low-carbon, but anyway it is only 0.02% of Demand i.e. is trivial. Geothermal plus hydro plus pumped storage *are* low-carbon, but together comprise a fairly trivial 0.13% of Demand.]

For Figure 2 I subtracted the sum of (Interchange + Nuclear + Geo etc. + Solar + Wind) from Demand each hourly data interval. This explicitly shows the hour-by-hour gaps between Demand and [fossil-free] Supply. I call this the [fossil-free] Shortfall and plot it in red.

Figure 2: TEX Generation and [Fossil-Free] Shortfalls- since Oct 23, 2024:

These results show that TEX is achieved zero hours of [fossil-free] power across this period - although it got close in daytimes in spring.

Throughout this period the lights didn’t go out across the TEX region. From this we know that the cumulative Shortfall (215.6 million MWh = 215.6 TWh i.e. 53.4% of Demand) was supplied by fossil generation.

We also see from Figure 2 that there were two very separate instances of maximum Shortfall, both of very similar size:
- the greatest Shortfall of -64,032 MWh/h in the whole period occurred February 18, 2025 [when TEX was experiencing one of its not-uncommon winter freezes];
- the other greatest Shortfall of -63,758 MWh/h occurred very recently i.e. in the hot season, on August 18, 2025.

Below, I look in greater detail at both these.

But first: what were batteries doing throughout the whole period? See Figure 3.

Figure 3: TEX Battery Discharging and Charging- since Oct 23, 2024:

In Figure 3 I deliberately plotted Battery discharging (blue) on the same vertical scale as Figure 1, so the relatively much smaller Battery power flows are clearer. I did the same with Battery charging (brown), but plotted it against the right hand axis to separate the two plots.

You can see that both plots have large numbers of points along and close to the zero axis, but with frequent spikes. Some Batteries are always doing something on the TEX grid. We can see this more clearly in Figure 3A where I have increased the vertical scales by factors of around ten.

Figure 3A: TEX Battery Discharging and Charging- Details:

As time has gone on, both the discharging and charging plots in Figure 3A have increased in magnitude, approximately doubling over this 10-month period. Time will tell whether this pace of change continues.

Winter and Summer TEX Energy ‘Crunches’

For both intervals of maximum Shortfall I zoomed in on the two weeks spanning the relevant dates. First, the maximum winter Shortfall of -64,032 MWh/h around February 20, 2025:

Figure 4: TEX, Maximum Winter Shortfall around Feb 20, 2025:

In Figure 4 you can see:
- Demand surged by about 30 GW between Feb 18 and Feb 20;
- Simultaneously, Wind dropped by about 20 GW across the same two days;
- Solar was barely reaching 10 GW to 12 GW on those two days;
- Batteries made no material difference to the energy balances each day;
- Peak need for dispatchable [fossil] power was 64 GW

All at a time when folks, and certainly their water pipes, might freeze without power2

The other largest Shortfall of -63,758 MWh/h occurred very recently i.e. in the hot season, on August 18, 2025, see Figure 5.

Figure 5: TEX, Maximum Summer Shortfall around August 18, 2025:

In Figure 5:
- Demand was reasonably steady between ~55 GW (nights) and 83½ GW (days);
- Wind dropped below 10 GW from August 18th through August 25th;
- Solar peaked at 27 GW on August 18th but of course fell to zero that sundown;
- Batteries made little difference to the energy balances each day;
- Peak need for dispatchable [fossil] power was 63.8 GW

At a time when temperatures were nudging 40°C3 (104°F).

What then for Future TEX?

“We expect rapid electricity demand growth in Texas and the mid-Atlantic” … “We expect electricity demand within ERCOT to increase by 7% in 2025 and by 14% in 2026 when some large data centers and cryptocurrency mining facilities come online.”

Considering we’re more than half-way through 2025 I’m guessing TEX is already coping with quite a bit of that 7% increment.

But another 14% next year…?4

Requiring more and more Solar panels (and grid reinforcements and *so much more* battery - or other - energy storage capacity, or [fossil-fuelled] dispatchable power, to keep the lights on every night when the Wind fails to cooperate)?

And if all the new generating *capacity* is ‘renewable’, will the costs of future ‘firming’ be allocated to Solar and Wind?
(I agree whole-heartedly with Professor Sir Dieter Helm - see especially his section “Are renewables cheap?” in that post - on this issue.)

Also, there’s the issue of recycling of end-of-life Solar panels. There’s going to be mountains of them: physically- and possibly chemically-hazardous; difficult-to-recover valuable components from amongst all the glass and plastic film; maybe only mostly recyclable using manual dismantling, crushing in hammer-mills, soaking in weak sulphuric acid and hydrogen peroxide for several hours; is that one of the new industries5 that’ll provide all those ‘green jobs’ we’re being promised?

As I said before: Good luck, Texas!

Copyright © 2025 Chris S Bond

Disclaimer: Opinions expressed are solely my own.

This material is not peer-reviewed.

I am against #GroupThink.

Your feedback via polite factual comments / reasoned arguments welcome.

2

Indicative TEX temperatures: Dallas/Fort Worth, February 2025:

3

Indicative TEX temperatures: Dallas/Fort Worth, August 2025:

5

Except as of 31 August 2025, open the link to the website and we find this message:

I guess that answers my question. It’s “NO”.

The storm-force winds covered the area of the UK which is already over-endowed with Wind *capacity*1 but under-endowed with transmission to the south [and also under-endowed with major Demands - a situation due to get worse if INEOS abandons Grangemouth because of hostile energy policy and costs]. As a consequence, lots of generation was Constrained / Curtailed, at a cost said to be over £30 million just in that one day.

I’ve seen it argued that the solution to high Constraint payments to Scottish Wind farms in such circumstances is to increase the capacity of the grid connecting Scotland to the south. That’s probably true in the short term, but it doesn’t solve the ultimate constraint in all electricity systems:

Supply MUST equal Demand every minute of every hour of every day

‘Surplus’ electricity must be constrained near-instantaneously, as must ‘Shortfalls’ be supplied. Otherwise the grid frequency varies outside its tightly-controlled limits and, if not corrected in real time, the grid or parts of it can ultimately fail.

So, further to my Over-Abundant Wind post from late 2024, and using the methodology I explained in my my Great Britain Reality post from January this year, I’ve looked into what the GB fleet of Wind plus Solar PV2 was doing over a period of a month spanning the days of Storm Floris.

Figures 1: The Gridwatch Dashboard as of 11.30 on 17th August:

The whole dashboard is shown on the left; I zoomed in on the week and month views of Demand, plus Gas, Wind and Nuclear in the middle; and on the right are zoomed views of that week and month of Hydro, Pumped, Biomass and Solar.

Note we are being propped up massively and near-continuously by mainly French and Belgian Nuclear plus Norwegian Hydro [see the charts on the far right of the whole dashboard view] via interconnectors [long may they remain undisturbed by dragging anchors].

I propose two handy rules of thumb when looking at the Gridwatch dashboard and wondering whether HMGov’s ‘net zero’ plan will keep the lights on without dispatchable power generation:

1. In summer when Demand is ~20 to 35 GW (as shown in Figures 1), all the time Wind is less than about 5 GW the lights would be dimming or out every night;

2. In winter when Demand is ~40 to 50 GW, all the time Wind is less than about
   10 GW the lights would be dimming or out every long dark cold night.

But surely energy storage would keep the lights on…

The four pumped hydro schemes in the UK have combined power capacity of
2,828 MW and have different durations of full-power discharge capacities ranging from 4 to 21 hours:

Then there’s GB’s huge fleet of operating batteries…

HMGov keep a ‘database’ of renewable energy projects [csv] “RE PD-q1-Apr-2025.xlsx” last updated 5 June 2025. Filtering for ‘Batteries’ under ‘Technology Type’ and ‘Operational’ under ‘Development Status’ we find 124 records, of which 103 have Installed Capacity (MWelec) values which sum to 2,631.8 MW - see the bottom right corner of Figure 2.

Figure 2: GB Operating Energy Storage - Batteries:

HMGov don’t actually record the potential duration of this storage3, but I’ll be generous and assume 1½ hours average usable duration, from which I derive current operating energy storage capacity of batteries ≈ 3,948 MWh.

Adding the pumped hydro storage capacity gives 28,488 MWh total. I’ll be extra-generous and allow this all to act as long-duration energy storage (LDES) when I include it in my analysis of the subject month. First, the plot of Gridwatch Demand, with Wind and Solar generation profiles. [I explain my use of adjustment factors in my GB Reality post.]

Figure 3: GB Demand, Wind and Solar PV; 17 July - 17 August 2025:

Applying rule of thumb 1. from above, you can already see there’s multiple times just in this month where Wind dropped and so HMGov future energy policy is likely to fail. It looks like a substantial proportion of the Wind fleet was able to keep generating through Storm Floris [shaded].

Figure 4: GB Imports / Exports; and Shortfalls; 17 July - 17 August 2025:

Through ‘Storm Floris’ our grid operator NESO [National Energy System Operator, formerly known as National Grid ESO] managed to get Imports switched to Exports [purple plot] and there was no ultimate constraint Curtailment imposed during the storm. However, Wind generation remained high for several days after the storm and immediately the sun came out fully on 5th August and again on 8th and 9th August, there were [potential] surpluses of ‘renewables’ requiring GB-level ultimate constraint actions. You’ll see this better in the zoomed version, Figure 4A, where I’ve highlighted the positions of the [grey plot] ultimate constraint peaks in yellow.

Figure 4A: GB Imports / Exports; Shortfalls; and Curtailments; 17 July - 17 August 2025:

It appears that NESO didn’t achieve sufficient switching of Imports to Exports during those intervals… the peak [potential] surplus was about 6,150 MW, i.e. within the combined capacity of the interconnectors had they all been exporting at those times.

Figure 5: GB Shortfalls; and LDES; 17 July - 17 August 2025:

As stated in the footer of Figure 5, my LDES algorithm allows charging only when there is 'surplus' fossil-free generation available; and discharging to counteract a Shortfall only if the LDES has energy stored. Because the period before the storm was continuously in Shortfall the LDES would be continuously flat. It is only in those short intervals of non-Shortfall that any energy goes into the LDES, but it is quickly run flat again.

The peak of stored LDES energy on 9th August is 18,822 MWh at 15:45. This is less than total LDES capacity, and so on this very simple basis increasing LDES capacity would appear not to be a benefit. However, peak power being stored in LDES was 6,086 MW at 14:00 that day: this is over double the power rating of the pumped hydro schemes. Ooops!

Extrapolating to HMGov’s planned future *capacities* of Wind and Solar based on this short interval of data we can illustrate some likely problems.

Figure 6: Future GB Demand, Wind and Solar PV:

Solar peaks routinely burst up above the Demand plot [ultimate constraint triggered];
but there are extended intervals where Wind is less than or much less that Demand, so when the sun goes down the lights would go out [please don’t call these intervals ‘dunkelflaute’ in July-August: there’s nothing ‘dark’ about this season and these Wind lulls are far from uncommon in GB summers].

Figure 7: Future GB Imports / Exports; and Shortfalls:

Unsurprisingly, for quite a lot of this period in July-August, GB would be struggling to keep the lights on unless we retained around 30,000 MW of fossil-fuelled generation capacity. Maybe an extra 5,000 MW of interconnector capacity could be built by the end of 2030 given more massive incentives by DNZ, but I really doubt our close neighbours are going to be able or willing to keep propping us up to anything like the extent needed to make Ed Milliband’s envisaged future numbers add up.

Figure 8: Future GB Shortfalls; and LDES:

Even if the existing energy storage fleet could cope with the MW energy flows [it couldn’t, as mentioned above] it doesn’t help much. Most nights it would go flat, but then at windy times it would fill up and stay full.

What if we doubled LDES capacity, i.e. added another 28,488 MWh of battery energy storage systems (BESS)? Then we’d get Figure 8A.

Figure 8A: Future GB Shortfalls; and 2 x LDES:

Not a huge difference from Figure 8, is it?

What would that mean financially, using as our basis the very current Statkraft Thornton project mentioned in the notes?

Our extra 28,488 MWh of additional storage energy capacity would be 28,488/400 times that project’s 400MWh, i.e. 71 times. Hence roughly 71 times its £150 million for additional battery energy storage.

Over £10 billion.

While all the time having to retain much of the fossil-fuelled generation capacity for those times when the Wind drops almost completely all across our interconnected region.

More evidence, I suggest, pointing to UK energy prices continuing to rise, regardless of politicians’ promises.

Copyright © 2025 Chris S Bond

Disclaimer: Opinions expressed are solely my own.

This material is not peer-reviewed.

I am against #GroupThink.

Your feedback via polite factual comments / reasoned arguments welcome.

I’m bringing the strands together here in this post to explain what I’ve learned.1

First, to make explicitly clear: David uses the 7-day NEM data at ½-hour intervals as the basis of his work. On X each week he publishes what I refer to as “three-year average squiggle-woo” together with boiler-plate text he probably hasn’t materially changed in the last couple of years, and of course a reference to his Renew Economy article of Aug 23, 2023. The squiggle-woo charts are distractions. To understand what he’s doing, we need to focus on his ‘7 Days…’ and his ‘28 Days…’ charts.

David’s latest “simulation” is for [week ending 09 July 2025] where he claims:
“Last 7 days = 99.1% RE, Last 202 weeks = 98.5% RE” … see Figure DO 1
[RE = renewable energy]

Figure DO 1 - 7 Days to Mid-09 July 2025: 99.1% RE

Running energy balances for the same 7 days of ½-hourly NEM data, I get 94.6% RE, see Figure CSB 1.

Figure CSB 1 - Same 7 Days to Mid-09 July 2025: 94.6% RE:

I’m using the same scale factors: Wind 4.2, Utility PV 2.5, Rooftop PV 1.9 2

But I get a significantly lower % RE.

Why?

Where is David getting all his extra ‘renewable’ energy from?

Perfect Foresight

David’s frequently-referenced Renew Economy article *does* include, way down at the bottom in FAQ 3, the following:

“Does your model assume perfect foresight? For the first 6 days of each 7-day simulation, my model assumes 24 hours perfect foresight. That is, it knows exactly what the wind, solar and demand will be 24 hours in advance. AEMO can reasonably accurately predict these quantities 24 hours in advance (and beyond), though not perfectly. For the last day of my 7-day simulation, the length of the perfect foresight linearly reduces to zero hours.”

And in his long X thread defending his “simulations” against Aidan Morrison, he included this:

Figure DO PF 1:

What does that means in real terms? Look at Figure DO 2. In the first three days, quite a bit of Hydro and ‘other’ fuel are being used at the same time as the Solar peaks. Then the same pattern of counter-intuitive use of Hydro and ‘other’ at the same time as the Solar peaks on a number of days including the several days beginning 26/06/2025. All to keep his energy storage charged up, to keep battery energy available for the following days when the “simulation” has perfect foresight of forthcoming periods of low Wind.

Figure DO 2: “Weeks 199-202, 28 day average = 92.7% RE”

Compare with my analysis of the same 28 days shown in Figure CSB 2.

Figure CSB 2: Same 28 Days to Mid-09 July 2025: 87.6% RE

In my extrapolations I do NOT use any foresight. The adjustments to Hydro I make are in arrears, depending on whether the previous ½-hour interval has a RE Shortfall or [potential] surplus. Note how my energy storage (the black LDES chart along the bottom plotted against the right hand axis) goes completely flat much more frequently and for longer than David’s. And how I account for all the [potential] surplus energy that would have to be Curtailed to keep the NEM grid stable.

It all became clear after our interchange on LinkedIn, see Figure CSB PF 1.

Figure CSB PF 1: LinkedIn Exchange of Views

As you can see, I don’t think much of his use of ‘perfect foresight’ in his “simulation”. He mentions he uses it to reduce “the variability” of curtailment, but I am certain that it also reduces the quantity of curtailment. That in turn allows more RE to be useful i.e. to keep the lights on, and consequently boosts the %RE he can claim.

That’s where David is getting his extra ‘renewable’ energy from.

Note: the only ‘quantification’ of curtailment David offers each week’s set of X posts, is in the bar chart for all weeks of his “simulation”, i.e. utterly useless for cross-checking.

Half-Hourly Adjustments to Hydro [in Arrears]

Instead of David’s ‘perfect foresight’ approach, my energy balances vary Hydro ½-hour by ½-hour according to what happened in the previous ½-hour, as follows:

Future Hydro = 1.5 times actual Hydro if the previous ½-hour interval has a Shortfall, but with upper limit 6,410 MW3;
or Future Hydro = 0.5 times actual Hydro if the previous ½-hour interval interval has a Surplus.

Then if Supply > Demand in that interval, the energy storage can be charged, but once it is full any surplus must be curtailed to keep the grid in balance.

Figure CSB 2: ZERO Foresight, 28 Days to Mid-09 July 2025: 87.6% RE

You can see the results of my approach in repeated Figure CSB 2, above.

For the 28 days ending midday 09 July 2025:
- Future Hydro = 8.1% of Demand, annualised to 19 TWh per 365 days;
- [nominal] future Wind + [nominal] future Utility Solar + [nominal] future Rooftop Solar (i.e. all before Curtailment) = 64.1% + 14.4% + 14.4% = 92.9% which added to the 8.1 % from Hydro = 101% … isn’t it a rule of thumb that you need around 20% over-capacity of ‘renewable’ generation?
- Curtailment is 2.15 TWh i.e. 12.0 % of Demand, and
- Fossil-free ‘Renewable’ generation is over 2.2 TWh i.e. 12.4% Short of being able to satisfy Demand, hence RE = 87.6% over this 28 days.

All David’s “simulation” has to do is move approximately half of that Curtailment across into the useful RE column as if by magic and, hey presto! he gets his claimed 92.7% RE4

All it needs is perfect foresight for 16 hours into the future, every day…

Polish up your crystal balls, folks!

AEMO and Perfect Foresight [for Storage Devices]

After my “Another 28 Days Later” post I was sent a link to the Australian Energy Market Operator (AEMO) Draft ISP Methodology: “Addressing perfect foresight for storage devices in the time-sequential model” [pdf] Published: 1 April 2025

“The intention of this paper is to provide additional context and analysis for the topic of modelling imperfect foresight for storage devices.”5

“Current forecasting and planning models are optimised with perfect foresight of supply and demand conditions within each day and across the simulation horizon. This allows perfect energy management and ideal intra-day dispatch of storage technologies.6 Actual NEM dispatch is dynamic and battery operators make dispatch decisions with less certainty about market conditions in future periods of each day.7
The risk management involved in deciding whether to dispatch energy now or wait for a potential higher price later, may lead batteries to bid and be dispatched at lower discharge rates or not at all, even if the current price is above a reasonable price thresholds.8

To better represent the potential for suboptimal dispatch outcomes of storage devices across the modelling horizon and provide insight into the impact of imperfect foresight on the reliability and operability outcomes, particularly ahead of long winter periods of high residual demand, AEMO proposes to incorporate two alternative approaches into the time-sequential modelling that supports the ISP:

• Headroom and footroom reservation – a small margin of energy at the upper and lower states of charge is reserved under most circumstances but remains accessible if required by the market. This reflects a proxy for operational risk mitigation strategies that preserve the option for storage devices to respond flexibly (either charging or discharging) to a future unforeseen event should it arise, and restricts storage devices from using its full capacity of stored energy on a daily basis.

• Deliberate energy planning error – energy storages are modelled with an explicit target operating plan, formulated with alternative assumptions of generator outages, interconnector outages, availability of renewable energy, and demand conditions. In this approach, storage devices would plan their states of charge according to these alternative system conditions. As a result, when an unexpected period of energy scarcity occurs due to unpredictable events, operators will not have had the foresight to have stored energy levels in advance of the unpredictable circumstance.”

Congratulations, AEMO, you’re re-inventing Design Margins!

Copyright © 2025 Chris S Bond

Disclaimer: Opinions expressed are solely my own.

This material is not peer-reviewed.

I am against #GroupThink.

Your feedback via polite factual comments / reasoned arguments welcome.

In case you’re unaware, the headline question is directed at The Rt Hon Ed Miliband MP, Secretary of State for Energy Security and Net Zero, who holds a BA in Philosophy, Politics and Economics from Oxford University and an MSc in Economics from the London School of Economics.

This post is a follow-up to my Great Britain Reality post from January this year. To avoid repetition I leave you to browse that post for all the background to this one.

For this post I’ve downloaded GB power data for the first six months of 2025 from Gridwatch.

Figure 0: The Gridwatch Dashboard on 01 July 2025:

I’ve then processed this data using a copy of the ‘2024’ file I used for the ‘G B Reality’ post linked above, i.e. using all the 2024 adjustment factors and multipliers as explained there.

The downloaded set of Gridwatch data comprises GB energy flows recorded every 5 minutes i.e. 5/60 hour. From this I can plot Demand versus the other key parameters as in Figures 1.

Figures 1: 01 Jan thru 30 June 2025 per Gridwatch:

I discovered there was a short gap in the data between 2025-03-17 19:05:32 and 2025-03-20 19:20:32, but this is only 3 days (less than 1% of a year). I have just adjusted how I pro-rata-ed to 365 days to get a first indication of likely energy quantities in the brave new ‘decarbonised’ GB.

Note: in the total energy balance tables appearing on the Shortfalls with LDES charts, I have used labels “[nominal] Wind” and “[nominal [Solar]”. This is because
Generation = Demand *every* minute of *every* hour of *every* day
The future extrapolations produce arithmetic results (future Wind + future Solar > Demand on ‘good’ days, and vice-versa) which are nonsense on stilts - grid stability demands all surpluses or Shortfalls are corrected in real time:
- [nominal] Surpluses that cannot be dispatched to empty energy storage or other reliable schedulable Demand would have to be constrained = curtailed;
- Shortfalls would have to be filled by dispatching controllable energy storage (if available) or controllable fossil generation;
- I refuse to accept ‘Demand Management’ as an option because it is ‘de-industrialisation’ by a different name.

Before I can extrapolate to a future scenario via Demand, Wind and Solar multiples, I have to adjust the raw Gridwatch numbers to get closer agreement of total energy from each source with the most-recently-available official record (DUKES). All as explained in the ‘G B Reality’ post.

Figures 2: 01 Jan thru 30 June 2025, Adjusted to ≈ DUKES:

As you can see in Figures 2, GB is getting close to having sufficient ‘renewable’ energy on good-weather days so as to reduce Shortfalls to ~ zero on those occasions. However, we do rely on power imports of up to ~10 GW at times via the interconnectors.

Into the Future

So, let’s see how this half-year of real weather-dependent power generation looks when we extrapolate to end-2030 via Wind and Solar (and Demand) multiples.

I make the gross assumption1 that, despite its dithering and general ineptitude, HMGov will by the end of 2030 still have the same largely CO2-free nuclear generation capacity as we have now.

Figures 3: 01 Jan thru 30 June 2025, Extrapolated to Dec 2030:

Note the extreme peaks of both Wind and Solar, and the rate of change of both, in the left chart. All the sources of ‘firming’ will have to ramp as fast to keep the lights on.

I have assumed for simplicity that imports & exports (centre chart) remain as-is.
(It is possible that by December 2030 more interconnectors will be operating, although it’s worth noting that Norway for one is pushing back against selling its precious carbon-free Hydro [paywall] at the same time its citizens are growing increasingly resentful of importing high European energy prices. But the sheer magnitude of the UK’s future [potential] surpluses and Shortfalls means that interconnectors are never going to have sufficient capacity to cope anyway… and that’s ignoring the introduced energy security risks with undersea infrastructure vulnerable to dragging anchors (or worse). It’s also probable, weather systems being the large-area phenomena they are, that the opposite parties in Scandinavia or Northern Europe would be enjoying similar weather-dependent gluts and Shortfalls at roughly the same times.)
The centre chart shows the peak power Shortfall is 50,000 MW = 50 GW. That’s the total capacity of the ‘firming’ (likely from gas turbines) that would be needed to keep the lights on in the worst circumstances this half-year. The peak Shortfall occurred 22nd January at about 6pm when Solar was zilch. (I discuss below what difference a credible capacity of energy storage would have made.)

The right chart (wherein note: power flows are converted to MWh per 5-minute interval) assumes that the total existing capacity of energy storage in the UK (currently comprising mostly pumped hydro, plus some batteries) could be dedicated solely to storage and discharge of fossil-free energy to mitigate against fossil-free Shortfalls. I know it doesn’t operate that way now, but it illustrates the reality of just how minimal it is.

The energy balance from the right-hand chart in Figures 3 is shown in Table 1.

Table 1: GB Energy Balance, December 2030 - Unchanged LDES:

Using first-half GB data and extrapolating to December 2030 according to what I understand is NESO’s plan (see my ‘G B Reality’ post for a discussion around that), it looks like GB will need just over 19% of Demand to be generated by fossil-fuelled sources… otherwise the lights would go out… frequently.

Figures 4: Extrapolation to Dec 2030, Varying LDES Capacity:

In the charts in Figures 4 the peak Shortfall is unchanged with the change of LDES capacity: in each case it is -4,190 MWh per 5 minutes (i.e. just over 50,000 MW ~ 50 GW, the same as remarked above). This is because 22 January was at the end of a low-Wind interlude lasting a week. By the end of such a long-duration lull, quite typical at almost any time of the year, any credible capacity of LDES would go flat as a pancake so there would be no stored energy to mitigate the Shortfall. Only some extremely dramatic and unlikely advances in cheap energy storage in the next 5-6 years could even begin to change that result.

The energy balances from the charts in Figures 4 are shown in Table 1 above, and Table 2 and Table 3 below.

Table 2: GB Energy Balance, December 2030 - Doubled LDES:

GB will still need just over 18% of Demand to be generated by fossil-fuelled sources if we could somehow double the available capacity of long duration energy storage (LDES) by December 20230 and dedicate it solely to storage and discharge of fossil-free energy to mitigate against fossil-free Shortfalls.

Table 3: GB Energy Balance, December 2030 - Quadrupled LDES:

… this would fall to just over 16% of Demand generated by fossil-fuelled sources if GB could somehow increase by four times, the current available capacity of long duration energy storage (LDES) ... etc.

None of those results are remotely close to NESO’s planned 5% fossil generation by the end of 2030.

I wonder, has 2025 thus far been an unusually uncooperative year, weather-wise?

Or are the ever-increasing constraints / curtailments showing themselves in the overall quantities of useful generation?

Time will tell.

Subsidies to Date

The GB ‘renewable electricity’ subsidy regime has, over the last 20+ years, paid out around £220 billion (in 2024 prices), all of which ultimately ends up in our power bills. This is equivalent to nearly £8,000 per household over that ~20 years. The Renewable Energy Foundation analysis shows that the total subsidy cost per unit of ‘renewable’ electricity generated is approximately £200/MWh currently… in addition to whatever the facility owners are paid for the power they produce.

Final Thought

Last but not least, to show GB bill-payers it’ll all be worthwhile... a reminder of how the rest of the world is eagerly following the path HMGov is demonstrating with its inspirational leadership2 and unswerving commitment3.

Copyright © 2025 Chris S Bond

Disclaimer: Opinions expressed are solely my own.

This material is not peer-reviewed.

I am against #GroupThink.

Your feedback via polite factual comments / reasoned arguments welcome.

This is a comparison with David Osmond’s [week ending 18 Jun 2025] X post where he claims: “Here is the simulation from weeks 196 to 199. It was 95.0% renewable.” Running energy balances for the same 28 days of NEM data, I get a significantly lower percent ‘renewable’, see below.

From the first post in that thread covering 11th-18th June 2025, he shows he used scale factors Wind 4.2, Utility PV 2.5, Rooftop PV 1.9. So in my analysis below I’ve done likewise.

But from another post in that thread: “The simulation has used wind, rooftop & utility solar data from OpenNEM, rescaled to supply ~60%, 25% & 20% respectively over the year. It uses the storage & existing hydro to match demand. If there remains a shortfall then the model supplements generation with ‘Other’”. My bolding on the “existing hydro” because in separate X DMs he told me that in fact his “simulation” re-allocates Hydro from times of surplus RE to times of Shortfall.

But how it does so is completely opaque. He kept pointing me to his Aug 23, 2023 Renew Economy article instead of answering numeric questions about his last “simulation”.

So, ok, I’ll show him mine (my numbers) in the hope that he’ll show me his (numbers, for the avoidance of doubt).

My analysis in this post is based on NEM ½-hourly data 21 May 2025 12:00 to 18 June 2025 12:00 which I’ve collected over the last several weeks. This period is featured in DO’s X-post per Figure 1.

Figure 1: DO’s “Weeks 196-199, 28 day average = 95.0% RE”

For reference, because I think it always helps to show where we’re starting from, I’ve plotted the key parameters from the 28 days of NEM data in the plot below. I’ve calculated the numeric totals (MWh) for all the sources of NEM generation, and the percentages they satisfied of the period’s total Demand, see the tables at the foot of Figures 2A & 2B.

Figure 2A: NEM Data and Energy Totals, 21May-18June 2025:

Note: the calculated round-trip efficiency of the Australian fleet of battery storage is 81.1% as shown at the bottom. For simplicity in my calculations with storage I use 80%.

You can see that Hydro, the blue line in Figure 2, is being varied (daily). Hydro generation is increased in the nights i.e. between the surges of Solar generation. It also looks like Hydro has larger variations when there is a Shortfall of Wind, smaller variations when Wind is in excess.

Maximum Hydro in this 28 days is 5,566 MW; arithmetic average Hydro is 1,932 MW; minimum Hydro is 363 MW; and total Hydro generation across the 28 days is 1,299,446 MWh ~ 1.30 TWh ~ 7.6% of total Demand.

Figure 2B: NEM Data and Overall Energy Balance, 21May-18June:

The charts are the same in Figures 2A & 2B, while the tables beneath them are different:
- in Figure 2B I have only included the major NEM sources amounting to 99.4% of the total along the lower left;
- in the middle we see the relative contributions of Hydro, Wind, Utility Solar and Rooftop Solar; and
- on the right the overall energy balance results: 36.7% ‘renewable energy’ RE.

Next, we can look ahead. Of course, we’ll never have an exact repeat of all this weather in the postulated future. But it’s useful to get an indication whether ever more windmills and solar panels could power an industrial economy. David Osmond keeps telling the world that it’ll be both easy and cheap. I’m running my analysis on the same generation data to see if I agree with the ‘easy’ part.
Seeing the basis of some of David’s costs, I very much doubt the ‘cheap’ part.1

Figure 3A: Future NEM, DO Scale Factors, Unchanged Hydro:

Figure 3A shows the charts with the David Osmond scale factors applied but with no adjustments to Hydro. Note I label the Wind and Solar totals in the lower right as “Nominal Future”… because without Demand or empty energy storage available, any surplus generation would have to be curtailed to keep the grid frequency stable. And you can only determine *that* by performing logical tests on each relevant parameter ½-hour interval by ½-hour interval - see the algorithm outline below Figure 3B. This is the arithmetic equivalent of the grid operator controlling generation must equal Demand in real time.

Straight away you can see that DO’s scale factors result in Nominal Future Total H + W + US + RS = only 102.7% of Demand across the 28 days. That’s a very thin margin to hope that that 7.6% share of Demand provided by Hydro could realistically be boosted to fill the gap.

You can also see more clearly in either Figure 3A or Figure 3B, how existing Hydro has been varied by the grid operator. Higher Hydro peaks [blue chart] correspond with Shortfalls [red chart]; higher Wind [green chart] *and* lower Hydro correspond with future LDES being fully charged [black chart], i.e. RE being in [potential] surplus.

Figure 3B: Same Hydro, DO Scale Factors, Future Energy Balance:

Logical Tests = Physical Limits Algorithm

The overall energy balance in the bottom right corner of Figure 3B shows the results after performing logical tests ½-hour interval by ½-hour interval as time progresses through the entire 28 days:2
- is RE > Demand? No
- then is there energy in LDES? Yes
- then use that stored energy to counter the Shortfall, and reduce stored energy by amount {[reduction in Shortfall that ½-hour, MW * 30/60]/ RTE} MWh
- and so on until LDES is zero, then there’s no stored energy to counter a Shortfall, the ‘battery’ is flat…
until
- is RE > Demand? Yes
- then is there empty capacity in LDES? Yes
- then use RE to satisfy Demand and use surplus RE to charge energy storage
until
- is RE > Demand? Yes
- then is there empty capacity in LDES? No, the ‘battery’ is full
- then use RE to satisfy Demand and CURTAIL surplus RE
until
- is RE > Demand? No
and so on.

After doing these step-wise calculations to constrain the system within the physical limits of the Future NEM with 120,000 MWh of energy storage (batteries or pumped hydro energy storage or a mixture of both):
the overall percent Shortfall = -11.4%
i.e. overall 88.6% renewable energy (RE).
Hydro generation in that 28 days is 1,299,446 MWh
= 7.6% of Demand
[Note: Demand is unchanged from current, i.e. zero allowance for ‘electrifying everything’, population growth, etc.]
Annualised, that Hydro would be 16.94 TWh, to be compared with the last actual year’s Hydro = 13.536 TWh. Also from that last actual year’s records we can see that maximum Hydro was 6,410 MW, so I’ve used that as the upper limit to Future Hydro when I’ve adjusted Hydro below.

Thus in this 28 days, recorded Hydro generation was already at an above-average rate.

Future NEM with Adjusted Hydro

Let’s see the effect of vary future Hydro, ½-hour by ½-hour, according to what happened in the previous ½-hour, as follows:

Future Hydro = 1.5 times actual Hydro if the previous ½-hour interval has a Shortfall, but with upper limit 6,410 MW;
or Future Hydro = 0.5 times actual Hydro if the previous ½-hour interval interval has a Surplus.
I repeated the analysis while again performing the Logical Tests = Physical Limits algorithm ½-hour interval by ½-hour interval as time progresses through the 28 days to satisfy grid stability etc. ultimate constraints.

Figure 4A: Future NEM, DO Scale Factors, Adjusted Hydro:

You can see I have deliberately and explicitly plotted a chart (grey markers, dashed line) showing the Curtailed generation. You can see this Curtailment only appears when LDES is full *and* when Wind is High *and* especially when this coincides with the daily surge of Solar. I look at this in greater detail below, see Figures 6A & 6B.

Figure 4B: Adjusted Hydro, DO Scale Factors, Future Energy Balance:

Using the Hydro adjustment factors shown: 1.5 times when there is a RE Shortfall but limited to maximum 6,410 MW; 0.5 times when there is a RE surplus; we end up with 9.5% RE Shortfall from the overall energy balance, corresponding to 90.5% RE. Quite a long way short of Mr Osmond’s claimed “95.0% renewable” in this same 28-day period.

His ‘Storage Levels’ chart has similarities, but also significant differences:

Remembering that adjusted Hydro across this 28 days would total 1,518,511 MWh i.e. 8.9% of Demand, equivalent to an annual usage of 19.79 TWh. That is nearly 1½ times the overall rate of last year’s total Hydro generation. I’m guessing Aus is unlikely to ‘burn through’ scarce Hydro at that rate, but even if it did the RE percentage would be lower than DO claims.

Note how, in my analysis, the energy that must be Curtailed totals up to 2,142,089 MWh. If, somehow, Mr Osmond’s “simulation” hides some of this away in a secret stash, then the difference might be explained. But his X posts don’t provide any transparency over his numbers, or whether his “simulation” abides by all the physical limits of the energy system.

Let’s zoom in on the last 7 days, midday 11th thru midday 18th June 2025.

Figure 5: DO’s “simulation”: last 7 days = 89.7% RE”:

I am puzzled at the peaks going above Demand. The dotted line is labelled “Demand + Charge”… but surely the “Charge” bit is already accounted-for in the rising ‘Storage Level’ plot… double accounting? Also, what’s with the burning of all that “Other” above the Demand line in the peaks of 11/06, 12/06 and 13/06…?
Curiouser and curiouser.

Anyway, here are my plots for the same 7-day period midday 11th to midday 18th June 2025. I simply re-scaled my charts to display those 7 days: all the numbers and analysis for the 21 days preceding midday 11th June are as I charted in Figures 4 above.

Figure 6A: 7 days on Future NEM, DO Scale Factors, Adjusted Hydro:

Of course I had to change the formulas used in the minimum, average, maximum and total tabulation along the bottom, to address only the data from the last 7 days.

Plotting the separate charts for Demand, Wind and Hydro and focussing on the nights, you can clearly see, for example, for overnight 11th-12th June:
- Demand is 30,000 MW falling to say 21,000 MW then beginning to rise again;
- Future Wind (i.e. actual Wind multiplied by DO’s factor 4.2) is about 6,000 MW to about 9,000 MW;
- Future Hydro is maximum 6,410 MW falling to about 4,000 MW;
- LDES goes flat shortly after the sun goes down;
- hence Shortfall is around 30,000 - 6,000 - 6,410 = -18,000 MW, rising (as Demand falls) to around 21,000 - 9,000 - 4,000 = -8,000 MW …

Or, for example, in the middle of the day on 16th June:
- Demand stays at around 30,000 MW;
- Future Wind is around 30,000 MW which alone the night before has exceeded Demand and so has charged up LDES;
- so after the sun comes up LDES capacity is quickly filled by shortly before midday;
- which is when any excess generation above Demand has to be Curtailed (there is nowhere else for it to go for grid stability to be maintained)

And so on.

You can follow it on my charts.

It’s opaque on David’s.

Here for completeness is the energy balance for this 7 days.

Figure 7B: Adjusted Hydro, DO Scale Factors, 7-d Energy Balance:

We end up with 14.6% RE Shortfall from the overall energy balance, corresponding to 85.4% RE.
To do so we need 10.2% of that week’s Demand to be generated using Hydro. Credible?

(By the way, if you look closely at my Hydro chart you can see it ‘jitters’ a bit when Demand and Supply are finely balanced. This is simply because my logic test ‘is there a Shortfall in the previous ½-hour interval’ flicks between ‘yes’ and ‘no’ and back. The overall effect on the results, however, is trivial: so I haven’t bothered to adjust it.)

Anyway, referring back to Figure 5:

I am puzzled at the peaks going above Demand.
The dotted line is labelled “Demand + Charge”… but surely the “Charge” bit is already accounted-for in the rising ‘Storage Level’ plot… double accounting?
Also, what’s with the burning of all that “Other” above the Demand line in the peaks of 11/06, 12/06 and 13/06…?

Over to you, David Osmond

If you have a RELEVANT polite technical argument to let me know where you think my ½-hourly energy balances are incorrect, please let me know. If you just want to deny without providing numerical evidence, or you wish to indulge in irrelevant obfuscation, I’ll ignore you.

P.S. for Peter Farley: Pumped Hydro Energy Storage ≠ Hydro

Copyright © 2025 Chris S Bond

Disclaimer: Opinions expressed are solely my own.

This material is not peer-reviewed.

I am against #GroupThink.

Your feedback via polite factual comments / reasoned arguments welcome.

1

DO’s Renew Economy article uses LCOEs as the basis for his ‘cheap’ claims - see his Table 3 below. As Prof Dieter Helm says, this “fantasy is … based on the elementary confusion of the marginal cost of electricity generated from a solar panel or a wind turbine with the system costs of firm power…” It’s worth reading “Full cost of electricity ‘FCOE’ and energy returns ‘eROI’” or the more recent “CATF – Beyond LCOE: A Systems-Oriented Perspective for Evaluating Electricity Decarbonization Pathways”

2

Detailed examples of my calculations for the last 22 hours of the period:

Columns B thru R are per the NEM download. All NEM data on CO2 emissions and costs are in hidden columns S thru AC. Column AD is a spacer.
Derived Columns are:
- AE simply repeats the NEM Date & time;
- AF = sum(C:R) of that row = Demand (MW) that ½ hour;
- AG = Future Hydro, adjusted according to the previous interval’s Shortfall (+ve or -ve);
- AH = Nominal Future Wind (excluding any necessary Curtailment);
- AI = Nominal Future Utility Solar (excluding any necessary Curtailment);
- AJ = Nominal Future Rooftop Solar (excluding any necessary Curtailment);
- AK = Nominal Future H + W + US + RS (excluding any necessary Curtailment);
- AL = Nominal Future Fossil-Free Shortfall (excluding any necessary Curtailment or available LDES action)

Further Columns:
- AN filters for potential surpluses, (MW) this ½ hour;
- AO filters for potential Shortfalls, (MW) for this ½ hour;
- AP is blank;
- AQ gives a nominal indication of energy going into or out of storage, without applying RTE or other logic steps;
- AR checks for a Shortfall and if there is sufficient energy stored in the LDES the interval before, uses it to act against the Shortfall. The quantity of energy used in doing so is increased by 1/RTE to account for storage round-trip losses;
- AS keeps track of the actual state of charge of the LDES, ensuring the maximum is limited to the available LDES capacity;
- AT shows the actual Shortfall after the action of the LDES;
- AU keeps track of Curtailed flows of power each ½-hour;
- AV shows some cross-checks on changes of LDES state of charge, MWh.

See my Eastern Australia Progress post for background, including on Australia's National Energy Market (the NEM) which operates the grid across Eastern Australia. That vast area comprises five States (New South Wales, Queensland, South Australia, Victoria, and Tasmania) plus the Australian Capital Territory.

See also, my critique of David Osmond’s weekly posts where he shows the results of running what he claims is “ a simulation of Australia’s main electricity grid using rescaled generation data to show that it can get very close to 100% renewable electricity with 24GW/120GWh of storage (5 hrs at av demand)”. Any energy system “simulation” like his, that substitutes 3-year-average squiggle-woo for a granular analysis of energy flows, isn’t going to show whether the lights would stay on or not.

Why

I’m not obsessed with Australia’s power generation despite any appearance to the contrary. It’s just that the Aussie continent is providing another real-life study into how practicable is a transition to mostly Wind plus Solar power generation in a wealthy industrialised society. Will it be enough to keep the lights on, and at what cost? Are there lessons to be learned from the Spain + Portugal blackout of 28 April 2025?1

Here in the UK over the last two decades or so, the similar drive to ‘decarbonise’ our power grid has been the be-all and end-all of Great British energy policy. Over the same timescale we, the home of the Industrial Revolution, have largely de-industrialised.

The policy of adding more and more Wind + Solar generation *capacity* also leads to Diminishing Returns, absent immense capacity of ultra-cheap electrical energy storage - which is yet to be developed at anywhere near adequate scale.

Is Australia dooming itself to follow the same path as the UK? Agreed, it is a *much* sunnier region than the UK… but so is Spain. Australia’s lights will still go out if it gets its energy policy wrong. And in the global context - see Figure 0 - would it make a material difference if Aus *did* ‘decarbonise’?

Figure 0: The Global Context of Carbon Emissions:

How

I’ve detailed my methodology in Appendix 1 below. It is all just simple arithmetic.

Current Status of the NEM

We can get an indication of the scale of Australia’s ‘decarbonisation’ problem from a one-year view taken from the Open Electricity website, see Figure 1.

Figure 1: The Current NEM Generation Mix for 1 Year:

Eastern Australia burns *a lot* of coal in a year; and the highest levels of coal consumption occur May - August i.e. in Australia’s winter months when Solar generation is lower.

Australia produces quite a lot of natural gas, but is liquefying and selling much of it to the rest of the world, leaving itself short of that flexible fuel. Meantime, Aus is going all-in on Wind plus Solar to bring its CO2 emissions down.

½-Hour Resolution Data

The granular NEM data2 I’ve collected begins 13 June 2024 00:00 and ends a full year later: from winter through an Aussie summer and back into winter. I have no idea how typical this year’s weather has been: this is the data I’ve got.

Figures 2: Real Power Flows, Five NEM States, 1 Year thru 14 June 2025:

In Figures 2, for each State I have plotted:
- the calculated in-State Demand (purple);
- recorded Solar (Rooftop plus Utility) (orange/yellow);
- recorded Wind (green);
- recorded Hydro (blue); and
- the calculated [fossil-free] Shortfall (red).
The vertical scale is the same for all: maximum 16,000 MW [set by NSW]; minimum -12,000 MW [to capture the worst-case in-State Shortfalls].
Plotting all States on the same scale clearly shows the relatively small magnitudes of South Australia’s and Tasmania’s power systems in the context of the whole NEM.
[Reminder: for my methodology see Appendix 1.]

Figures 3: The Five NEM States - Combined Generation and Shortfalls:

You will note in the right hand image in Figures 3:
- my calculated total Demand for the year is a little over 215,266,000 MWh = 215.266 TWh. The NEM year in Figure 0 shows Net Energy 215.251 TWh. That’s very good agreement and a good reality check;
- the summation of [total Wind] + [total Solar] + [total Hydro] + [-total {fossil-free} Shortfall] = 30.425 + 44.644 + 13.536 - (-125.661) = 215.266 TWh; again, a good check on my arithmetic.

This year of real data demonstrates how false is the belief that, across a land area as huge as Eastern Australia, there would never be times when there’s not enough Wind + Solar + Hydro together to keep the lights on. Every night, of course, Solar drops to zero; and that quite often coincides with Wind collectively falling across the region. Hydro output can be controlled to sometimes fill the gaps, but in drought-prone Aus, Hydro is a finite resource. And, of course, any pumped hydro energy storage in the system doesn’t generate extra electricity, it usefully time-shifts it while consuming round-trip efficiency losses.

Looking at the overall energy balance as revealed by this year’s numbers:
- combined Demand averaged 24,466 MW (max ~39,317 min ~17,063 MW);
- combined Wind averaged 3,458 MW (max 9,192 min 104 MW);
- combined Solar averaged 5,074 MW (max 21,419 min 0 MW *every* night);
- combined Hydro averaged 1,538 MW (max 6,410 min 190 MW).
These leave the fossil-free Shortfalls as follows:
- combined Shortfall averaged -14,396 MW (best -5,374 MW worst -26,351 MW)

For a **very preliminary indication** of how much more Solar + Wind *capacity* might be needed just to satisfy the average Demand of ~24,500 MW, the energy balance using the above average numbers gives:
three times average current Solar + Wind = ~ 3 x (5,074 MW + 3,458 MW) ~ 25,600 MW

Of course, averages don’t keep the lights on. So Australia will need a lot more than three times current Solar + Wind *capacity*, plus all the extra grid, transformers, etc. etc. … and that’s before accommodating future increased electrical power consumption as electrification takes place.

Magnitude of Storage Required to Moderate Solar

The extreme variations in Solar generation drive the extreme spikiness of the Shortfall chart. The extreme peaks in Solar generation also drive substantial and increasing levels of curtailment to allow control of grid frequency within the required tight tolerances. [Noting that curtailment can also be driven by local grid capacity etc. constraints, but the ultimate limit is Demand in that time interval.] The daily Solar ‘surge’ occurs over a 24-hour timescale and so, just in terms of that duration limit, Solar *should* be ‘easiest’ to moderate using electrical energy storage.

The NEM has begun this effort: at the time of writing it lists 39 “operating” battery energy storage system (BESS) facilities with total capacities 6,109 MW / 10,304 MWh - see Figure 4 below. [However, NEM’s definition of “operating” is too flexible: the largest - Waratah - is still barely doing anything3 six months after it first appeared on this list]

Figure 4: “Operating” Battery Energy Storage Systems on the NEM:

How big is the problem for the five States of the NEM? Let’s begin to see.

Figure 5: The Five NEM States - Summer Solar Generation Profiles:

High summer Solar MWh/d by State and date:
- S.Aus max = 21,853 MWh in 24h beginning 00:01 on 04 Dec 2024
- NSW max = 82,546 MWh in 24h beginning 00:01 on 20 Dec 2024
- Vic max = 39,997 MWh in 24h beginning 00:01 on 18 Jan 2025
- Qld max = 62,005 MWh in 24h beginning 00:01 on 08 Dec 2024
- Tas max = 2,301 MWh in 24h beginning 00:01 on 18 Dec 2024

For each State we can then find the MWh capacity of BESS required to smooth that maximum day’s Solar generation across that 24 hours as shown in Figures 6:

Figures 6: Moderating Solar for each NEM State Individually:

Summarising the results:
- NSW BESS ~50,000 MWh ~ 30 x Waratahs ~ AUD 30 billion,
for an average 3,439 MW smoothed power across that day.
- Vic BESS ~24,600 MWh ~ 15 x Waratahs ~ AUD 15 billion,
for an average 1,667 MW smoothed power across that day.
- Qld BESS ~39,250 MWh ~ 23 x Waratahs ~ AUD 23 billion,
for an average 2,584 MW smoothed power across that day.
- S.Aus BESS ~13,700 MWh ~ 8 x Waratahs ~ AUD 8 billion,
for an average 911 MW smoothed power across that day.
- Tas BESS ~1,400 MWh ~ 0.8 x Waratahs ~ AUD 0.8 billion,
for an average 96 MW smoothed power across that day.

Always remembering that you get back less energy from a BESS: they are not ‘electricity generators’, they are ‘electricity time-shifters’ with losses.

And remembering that these are for current recorded rates of Solar generation. In the future, whatever the multiple of Solar *capacity* gets installed, those BESS capacities and costs will need to be multiplied by the same factor(s).

Note I’m not claiming the above would represent the best use of BESS capacity. They simply illustrate the magnitude of BESS capacity required to smooth each peak day’s Solar in each of the NEM States.

Figure 7: Alternatively, Moderating Solar for the Combined NEM States:

If we assume that the interconnection capacities between the five NEM States are without limits (unrealistic), then if they pooled their BESS capacities to smooth the maximum combined Solar from the peak day of summer 2024 - 24 December 2025 - then the total BESS capacity would ‘only’ be ~114,000 MWh ~ 68 x Waratahs
~ AUD 68 billion, for an average 7,932 MW smoothed power across that day.

Extrapolating Into the Possible Future

I’ve outlined my methodology in Appendix 1 at the bottom of this post.

The main parameters for a future ‘decarbonised’ NEM (assuming we have to continue to rule out carbon-light nuclear generation) are:
- future multiple of Wind;
- future multiple of [total Solar];
- future multiple of Hydro;
- future capacity of electrical energy storage (whether BESS, pumped hydro or other yet to be commercialised at scale)

What measure should we use to judge ‘success’? There are multiple variables and consequently too many possible outcomes to do anything more than illustrate the issues.

But first, eliminate one potential variable: assume future Demand will be higher.

Allow future Demand across the NEM to increase by a factor 1.5

to allow for increases in population, electrification of everything, and to try to ensure that power is sufficiently plentiful so as to prevent de-industrialisation.
I leave the financial modelling of the following scenarios to others, except to say I would expect a transparent discussion of *all* the costs versus benefits of any options.

I assume zero increase in Hydro across drought-prone Australia.

For each scenario below, I assume a repeat of the last year’s weather-dependent generation profiles. Of course, weather being weather, this might have been more or less benign than is typical, and almost certainly was not as adverse as a reasonable worst-case might be. That’s the thing about critical energy systems: they need to be designed to achieve ‘good’ performance whatever the weather brings.

Example Scenario 1: 120,000 MWh LDES, Lights on 80% of the Time:

The NEM could keep the lights on for 80% of the ½-hour intervals if there were in future:
120,000 MWh of electrical energy storage; and
7.4 times current Wind; and
4.4 times current [total] Solar.
To maintain grid stability, 118 TWh of power cumulatively surplus to Demand across all the ½-hour intervals would have to be curtailed.
This scenario requires just over 22 TWh of dispatchable [fossil] power generation, which is nearly 7% of the year’s cumulative Demand.

Example Scenario 2: 240,000 MWh LDES, Lights on 80% of the Time:

The NEM could keep the lights on for 80% of the ½-hour intervals if there were in future:
240,000 MWh of electrical energy storage; and
6.4 times current Wind; and
3.8 times current [total] Solar.
To maintain grid stability, 51 TWh of power cumulatively surplus to Demand across all the ½-hour intervals would have to be curtailed.
This scenario requires just over 25 TWh of dispatchable [fossil] power generation, which is nearly 8% of the year’s cumulative Demand.

Example Scenario 3: 60,000 MWh LDES, Lights on 90% of the Time:

The NEM could keep the lights on for 90% of the ½-hour intervals if there were in future:
60,000 MWh of electrical energy storage; and
11.0 times current Wind; and
6.6 times current [total] Solar…
But, to cope with the maximum surplus RE power flow into storage of over 56,600 MW this scenario would require the power capacity of about 25 times Snowy 2.0… but assuming sufficient LDES power capacity was made available,
to maintain grid stability, over 330 TWh of power cumulatively surplus to Demand across all the ½-hour intervals would have to be curtailed.
Meanwhile this scenario requires just over 9 TWh of dispatchable [fossil] power generation, or nearly 3% of the year’s cumulative Demand.

And so on: a near-limitless number of permutations can be postulated.

Note that a scenario achieving ‘keeping the lights on’ 80% of the time, equates to having over 40,000 MW of total capacity of dispatchable sources of power available to surge into action 20% of the hours ~ 1,760 hours in a year. Sometimes for just a few hours, sometimes for days. Sometimes hardly ticking over, occasionally all going flat out.

Similarly for the ‘keeping the lights on’ 90% of the time scenarios, except the near 40,000 MW of total capacity of dispatchable sources of power will only be called on ~880 hours per year, with similar huge variations in the rates they’ll need to be run at.

That ‘keeping the lights on’ power is society-critical. If that critical power is to be delivered when it’s needed, all that [ageing, unwanted but essential] fossil-fuelled generation capacity will have to manned, inspected, maintained, paid for… somehow.

Conclusions

Considering the huge quantities of minerals [pdf] that are required for 100% ‘renewable’ power generation4 I think we’re duty-bound to moderate our ambitions for ‘decarbonisation’ to a practicable level.

Whether the large multiples of Wind and Solar plus energy storage I outline above for the future NEM are ‘practicable’, only Australians can judge.

Appendix 1: Methodology

The NEM records data for the whole of the NEM, and also separately for the States within the NEM. The States have some power interconnections and routinely exchange power, and the NEM is planning to increase interconnection capacities.

At the whole-NEM level, interconnector power flows are opaque: download a set of NEM data and no inter-State power flows are reported, as you can see in the example week’s data below:

At the State level, however, interconnector power flows are reported. I have more confidence when I can see the data, and anyway I’m interested in progress at the State level, hence I perform energy balances State-by-State for each ½-hour interval. I then combine those individual State results arithmetically using the NEM time-stamps to keep the energy quantities in sync.

For the extrapolations to future-Australia I ignore grid limits. I’m very aware that grid power capacities are limited, but what I’m trying to do with my extrapolations is illustrate the *magnitudes* of the power flows as ‘electrification’ ramps up. Then readers can produce their own back-of-envelope costings for such grid expansions.

Similarly, I am agnostic as to how a multiple of Wind or of Solar should be delivered in the future. By that I mean the location, types, dimensions, nominal design *capacities* etc. etc. of all the additional hardware, are all irrelevant details to my analysis. I don’t care exactly how a Wind multiple of W or a Solar multiple of S is delivered. But I am certain that the details will heavily influence the costs. Again, once they know the multiples needed, readers can produce their own back-of-envelope costings for them.

a) NEM data for each State:

My workbook comprises several tabs: one for each NEM State, one for collected data, one for charts, etc.

Example data for NSW:

Example calculations for NSW:

Example Collection calculations for NSW:

The [fossil-free] Shortfall in a given interval =
Wind + total Solar + Hydro - [in-State Demand]

The only fossil-free energy source I omit is ‘Bioenergy (Biogas)’, which features only in the data of NSW and Queensland. A quick check reveals the contributions are minimal, typically less than 1%, i.e. are not going to materially change my analysis.

The sets of collected records and derived Demands and Shortfalls are the source of the plots for each State I show in Figures 2. At the bottom of each range of my Excel file are the calculations of Minimum, Maximum and Average of each parameter that are reflected onto the bottom area of each chart. These were complicated by a few NEM data anomalies at around 05/09/2024 14:00 which affected all the States - so my formulae do not include those few rows of anomalous values.

b) Extrapolated energy flows and energy balances for each State:

I designed the layout of the workbook to fully preserve the original data as described above, while allowing extrapolation using simple multiples in a different area of the ¦collected¦ tab.

Example future (extrapolated) calculations for NSW:

The same multipliers are used on each State’s data for each timestamp. As can be seen in the right image, as that day advances past noon the [fossil-free] Shortfall switches from -ve to +ve then back to -ve in NSW, and similarly but differently in South Australia.

Example future (extrapolated) calculations for the combined NEM States:

It’s all simple arithmetic. Each State’s recorded Wind or [total] Solar or Hydro times the relevant multiplier. The result compared to the multiplied Demand giving that interval’s Shortfall. All the Winds added together; all the [total] Solars added together; vs. all the Shortfalls added together.

Of course future reality would not be that simple: I have not tried to include for curtailment, I have not tried to account for grid limits, etc. My intent is simply to see how big the simple numbers get, and whether, having simply summed the numbers, the NEM’s lights stay on.

Example future (extrapolated) calculations for the combined NEM States - LDES:

Continuing scrolling to the right, we can see the rest of the calculations.
- the combined States future Demand
- the combined future Shortfall or surplus
- the long duration energy storage (LDES) calculations
[which assume the LDES begins at 50% charge to counter earliest Shortfalls]
- the LDES charging or discharging
[which assumes only surplus Wind + Solar electricity is used]
- curtailment required if the LDES has filled up, to maintain grid balance
- a counter for the number of ½-hour intervals of Shortfall despite the action of LDES
- a tally of total combined Hydro
[various commenters have said that more hydro is unlikely in low-rainfall Aus]

Always remembering that energy storage does not *produce* electricity, it only time-shifts it. The real-world mainly-battery round-trip efficiency (RTE) I’ve used in these calculations seems (from NEM data) to be around 80%. That energy loss is an overall drain on the system, but may be tolerable because it can shift energy from times of over-supply = curtailment, to when it’s needed.

End of Appendix 1.

Copyright © 2025 Chris S Bond

Disclaimer: Opinions expressed are solely my own.

This material is not peer-reviewed.

I am against #GroupThink.

Your feedback via polite factual comments / reasoned arguments directly relevant to the material in this post, are welcome.

4

“Estimation of the quantity of metals to phase out fossil fuels in a full system replacement, compared to mineral resources” by Simon P. Michaux: Bulletin 416 from Geological Survey of Finland. See for example the chart on page 228 [reproduced below] and the charts on pages 229-230.
I think a pragmatic approach with current technology might land at a solution with somewhere between 6 hours and 48 hours of energy storage, and so I think the purple and yellow bars are better indicators. Still, up to 3.3 times global copper production and up to 2.9 times global nickel production to date. Etc.