More Battery Reality in Texas

More than six months on from my previous TEX post, with more 'renewable' *capacity* plus batteries added, an update on ERCOT region power generation

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:

Note: the calculation of Shortfall includes the benefit of Nuclear

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:

Note: the calculation of Shortfall includes the benefit of Nuclear

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:

Note: the calculation of Shortfall includes the benefit of Nuclear

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!

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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.

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1. Note: NOT battery-powered. Batteries don’t produce power, they time-shift it at the cost of the loss of the round-trip efficiency (RTE) losses - which from the EIA data for TEX for this period runs to around 18% of the energy (MWh) stored.

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

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

4. The increment includes for ‘cryptocurrency mining facilities’? I would question the value to society of such facilities.

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”.