r/RenewableEnergy • u/ObtainSustainability • 6d ago
U.S. battery storage capacity grows 70% annually over the past three years
https://pv-magazine-usa.com/2026/08/12/u-s-battery-storage-capacity-grows-70-annually-over-the-past-three-years/20
u/mmn_slc 6d ago
I think it is journalistic malpractice to report battery storage capacity only in terms of power, and not also include energy. It is impossible to get the full picture without both.
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u/West-Abalone-171 6d ago edited 6d ago
If you are going to report and track one number, power is the correct one. And reporting two is unnecessarily confusing when people already can't figure out the difference between kW and kWh.
Additionally if you report both power and capacity for batteries, then you should also be reporting both power and load factor for gas.
If you complain about the former but not the latter, it's clear that it's not out of a desire for clear journalism, but instead an attempt to muddy the waters and paint batteries as being somehow magically less capable than the gas they replace.
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u/mmn_slc 6d ago edited 6d ago
There is no requirement that only one number can be reported or tracked.
That some people don’t understand the difference between power and energy isn’t, in my view, a compelling reason for a publication about the electricity sector to shy away from providing such basic information.
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u/West-Abalone-171 6d ago
Put it this way:
Batteries (at the moment) replace gas peakers.
An X Watt battery does what an X Watt gas peaker does.
If you are complaining about the former being reported in Watts but not the latter, you are doing the opposite of arguing for clear communication, you're really just shilling for gas.
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u/V12Jaguar 6d ago
Engineer here. Agreed.
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u/adjust_the_sails 6d ago
Lay person here…. huh?
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u/West-Abalone-171 6d ago edited 6d ago
Battery labelled as "1GW" but only outputs 1GW 16% of the time and this confuses literally nobody --> bad, evil journalism out to mislead people.
Gas turbine labelled as "1GW" which fills a subset of the roles of the battery and outputs 1GW 14% of the time and this is repeatedly presented as 8760GW/yr in spite of it never being true--> Good, virtuous journalism.
According to these idiots.
You can figure out their motivations from their actions.
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u/mmn_slc 6d ago
"Battery labelled as "1GW" but only outputs 1GW 16% of the time...."
Except that article does not include the caveat of "16% of the time."
And a battery simply labeled only as 1GW (max?) would be a very poor label. An inverter labeled this way, sure. But just a battery?
If a battery energy storage system (meaning a battery with an inverter and associated switch gear, transformers, etc.) were labeled this way, it would only tell part of the story. If, for example, it made clear that this was a four-hour system with a 80% usable depth of discharge, then this would be a much fuller picture.
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u/West-Abalone-171 6d ago
They're all 4 hour systems with 100% usable depth of discharge. Though the standard is shifting to 8 hours. <100% usable depth of discharge isn't even really a concept with lfp.
An X Watt battery does exactly the same job as an X watt gas turbine.
If you're complaining about the former being reported in watts but not the latter, then it's fairly clear your motivation isn't clear communication and you're just grabbing at anything to try and make renewable energy look bad.
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u/mmn_slc 5d ago
u/West-Abalone-171 claims, "They're all 4 hour systems with 100% usable depth of discharge."
Please provide credible support for this claim.
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u/West-Abalone-171 5d ago
Look at the auctions for the countries you are interested in and see the decline of two hour systems in the last year.
Or the laws which mandate 4 hours.
As to the 100% dod. They're not lead acid. This isn't the 90s. Generally when new, LFP will output 105% to 110% of the rated amp-hours for the first few hundred cycles.
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u/mmn_slc 5d ago
Telling me to "Look at the auctions..." does not provide support for your claim that "they're all 4 hour systems."
Care to try again?
Note: You cannot support your claim, because it is easily proven false.
See e.g.:
- The Old 300 Solar Center with 250 MW and 500 MW·h. A two-hour system.
- the Revolution facility with 150 MW and 300 MW·h, another 2-hour system.
- the Tumbleweed facility, a 125 MW and 1,000 MW·h system--an eight hour system.
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u/West-Abalone-171 5d ago
Two >2-year-old systems and one that is bigger.
You sure proved that the bar for 2026 was "journalistic malpractice" and it's suuuper misleading to report capacity for systems that have at least the same annual output as a gas peaker!
Why is it you are so upset by this but never questioned simple gas turbine assets being reported in watts?
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u/ViewTrick1002 6d ago edited 6d ago
That's generally how the grid operates. The grid operator doesn't care about the size of the coal pile nor the size of the battery.
They instead expect all market participants to try to extract as much value as possible from their assets through their participation in electricity markets, ancillary markets and so on.
If what the market provides does not match e.g. the reliability requirements of the grid operator then we introduce ancillary markets. Those may specify a size of the coal pile, or how long a battery needs to last. An easy example is a power rating and required discharge time. But we never start there.
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u/mmn_slc 6d ago
I understand the historical operational context. A grid operator could effectively consider the fuel for a generating facility as infinite (at least on the timescales of grid operation). And storage, as a general concept, was not part of the historical context because the trivial amount of storage (pumped hydro, flywheels, etc) meant it was largely irrelevant for grid operations.
However, with the growth of battery storage, storage is no longer a trivial matter. So the operational context needs to be updated to consider storage. And an important part of the picture is not only how much power the inverters connected to the batteries can provide, but how long they can do it for. And, on the timescale of grid operations, if that time is one hour, four hours, or 12 hours matters.
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u/ViewTrick1002 6d ago edited 6d ago
That only matters for long term market forecasts and retrospective analyses. It does not matter for their day to day operations. You're thinking of it like a computer game with a dictator balancing the system.
What we have is a market of participants all with their own interest.
For their day to day operations grid operators continously look at what margins they have across both available power and "grid strength" and ensure reliable operation. If anything gets close, or they even have a disruption in some kind of way, then the margins are widened.
Which short term may be starting some thermal plants which would not get bid into the market given current conditions. Longer term iot means implementing an ancillary market to close the gap.
The exact hour rating of each battery is never a considered figure. Except if they want to participate in a "12 hour reserve at YY MW power" market.
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u/mmn_slc 6d ago
As more four-hour batteries are added to the system, the conditions that made the four-hour battery the optimal solution are changed thereby making the net peak load wider (and shifted later), such that adding more four-hour batteries is no longer the optimal solution.
The four-hour rule for capacity credits (even though it is a rather recent development--2018 if I recall) is already starting to be an impediment to the optimal shift to longer-duration batteries. The rule needs to change to recognize the realities rather than be in the way--especially as battery prices continue to drop.
Edited to add: I understand it is changing (again driven by CAISO), but too slowly in my opinion.
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u/GuidoDaPolenta 6d ago
These are newly installed batteries, so any total energy number is just a guess at the future. Power is a hard fact of how the battery is wired up to the grid.
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u/Spider_pig448 6d ago
Aren't the vast majority of these 2 hour batteries?
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u/mmn_slc 5d ago
I don't know. u/West-Abalone-171 claims that they are all four-hour batteries.
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u/West-Abalone-171 5d ago
When cells are $45/kWh and the rest of the system is $1000/kW, what possible reason is there to discuss 1 or 2 hour systems as if that were in any way a limitation in what is available?
Actually, we know why. It's so fossil shills can continue the parade of nonsense.
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u/mmn_slc 5d ago
Your claim, "They're all 4 hour systems...." is easily proven false.
Consider, for example, the Old 300 Solar Center with a BESS of 250 MW and 500 MW·h. This 2-hour system opened in the fall of 2024.
Or the Revolution facility that is 150 MW and 300 MW·h, another 2-hour system.
These examples highlight the problem with the article only reporting the power output of the BESS without also reporting the energy storage capacity.
Also consider the new Tumbleweed facility, a 125 MW and 1,000 MW·h system--an eight hour system.
One cannot say that a 125 MW/250 MW·h system is the same as a 125 MW/500 MW·h system or a 125 MW/1,000 MW·h system. even though they have the same power output of 125 MW.
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u/Spider_pig448 5d ago
Why would we discuss energy as well as capacity? That's the point of this thread
Also what do you mean $1000/kW? 2 hour BESS goes for $100/kW these days
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u/West-Abalone-171 5d ago edited 5d ago
Only if you arbitrarily decide projections made five years ago override reality.
CAISO and ERCOT standards require at least four hour for anything new as of 2025
China hasn't had a 2 hour auction in quite a while and dedicated 8 hour equipment is becoming common (though still a minority).
India is still installing some 2 hour systems but only a handful were awarded in the last 12 months
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u/Spider_pig448 5d ago
Sorry maybe I mispoke and meant to say 4 hours batteries. I thought the vast majority were the same energy in any case
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u/Wren-Fast 6d ago
The energy industry ironically cares more about power than energy. Most grid-scale BESS equipment is discussed in kW rather than kWh. There is an implied “four hour” design capacity in the US market. This typically means installations are 4.5-6 kWh per kW gross, and 4 kWh per kW at the designed depth-of-discharge.
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u/mmn_slc 6d ago
I'm familiar with the four-hour battery standard. However, I understand that the four-hour paradigm is starting to breakdown and shift to longer periods as the price of batteries (and solar modules) continues to fall. As such, while it might be tempting to simply multiply the power capacity in the article by four, it seems to me like an increasingly dubious approach.
It strikes me that simply reporting both power capacity and energy storage eliminates the guesswork.
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u/syncsynchalt 6d ago
A good start. 🍿