California's Battery Array Is as Powerful as 12 Nuclear Power Plants

Two to four hours per day.

Source: https://www.energy.ca.gov/data-reports/energy-almanac/califo... under Additional Information about the Data:

> The use of the terms megawatts and kilowatts as descriptive of battery energy storage is to effectively convey the instantaneous power contribution of battery storage as comparable to the power produced by grid-level generators. We recognize that energy capacity in the context of energy storage typically refers to the total energy a battery can hold in watt-hours, kilowatt-hours, megawatt-hours, etc. However, for statewide planning and reliability purposes, understanding the peak power capability of battery energy storage systems allows for the integration of data with the nameplate capacity of traditional power generation units serving the grid. It is in this context that battery systems are able to be effectively compared for their ability to serve the grid over short periods of time, typically two to four hours per day depending upon system conditions.

I agree, this article is horrifically misleading.

An array of batteries discharging 12,000 megawatts for ... 5 minutes? 1 hour? 1 day? is not comparable to a nuclear power plant generating 1,000 megawatts continuously 24/7 for months without refueling.

Also batteries are storage. They do not generate electricity. They store excess energy produced elsewhere, by actual electrical generation facilities, then release it later. You can't compare batteries to actual power plants.

Seriously, watts aren’t energy.

That’s like saying “my gas tank can hold 500 horsepower”

> The batteries are [used] during the peak period, which is in the evening, typically around seven o’clock, producing as much as 40 percent of the peak capacity requirements.

In most countries the peak period is a 4-5 hour window.

This series of graphs shows grid batteries quickly displacing peaker gas plants in Queensland over 24 months / two years.

This isn't the most advanced grid in the country, but it's just good business to displace the most expensive and dirtiest gas plants even if you still use gas for other tasks on the grid.

https://reneweconomy.com.au/wp-content/uploads/2026/05/open-...

The net storage graph clearly shows they aren't drained empty after 3 hours. They keep their remaining charge for the more expensive morning peak rather than compete with cheap imports overnight (there's a graph showing the cost over the time range too).

California's demand commonly goes from 18GW to 30GW in the same day.

Lets take your smallest "Nuclear plant" idea, if California owns 6 of those they run all the time but it needs 12GW extra at peak, where does that come from? If California owns 10 of those they run intermittently, you're still paying to have ten but not getting almost twice the benefit so your prices soar.

So the way you'd presumably fix it would be to... build loads of storage and own say 9 of these 3GW nuclear plants, drawing from batteries at peak then refilling them overnight. But wait, that's already what California did that you're unhappy about - so what gives?

Then we notice that in reality although you think "most nuclear power plants" would produce 3-6GW in fact California doesn't own ten, or eight, or six, but one such plant and it produces... drum roll... 2.2GW nameplate.

Batteries must always be talked about while mentioning both the stored energy and the maximum power.

These 2 battery parameters depend on different constructive details of the batteries. The stored energy depends on the volume of the electrodes (or of electrolyte in flow batteries), while the maximum power depends on the area of the electrodes.

All combinations are possible, e.g. batteries with high maximum power and low stored energy or with low maximum power and high stored energy or with both high maximum power and high stored energy.

In practice, it can be very relevant. With my own household solar/battery system, I am sometimes frustrated more by limits on how much current I can draw, not by capacity. I could add more batteries, but it seems that the inverter is the limiting factor. And 12MW of inverter is impressive, no?

They use power units to make it comparable with the non-storage sources, see https://news.ycombinator.com/item?id=48157824

We already do.

https://www.blackridgeresearch.com/blog/latest-list-top-larg...

https://electrek.co/2026/05/11/uk-delivers-europes-largest-v...

UK is up there in the world rankings for batteries.

I think they have slightly more grid batteries installed than California. UK have more people, but less money and less electricity used so I'd say they're doing better than California on battery deployment.

California imports a third of its electricity, and that's expensive. It gets almost another third from natural gas. They've been changing rapidly from fossil fuels and nuclear to renewables and that's pretty capital intensive. And there have been some huge costs associated with the wildfires.

There's a bit more technical info on California battery storage here:

https://www.ess-news.com/2025/04/11/california-battery-domin...

Paying for wildfires is a big part of it.

Another less obvious thing is that Californians don't use much electricity due to mild climate and efficiency programs.

Fixed costs therefore get spread across fewer units.

This is a topic in some nations where electrification is seen as a way of driving down per unit electricity costs even as you use more for heating or transport.

> Just for a moment, try to imagine how much wind, solar and battery storage can be bought with the money required to build just one regular nuclear power plant (gigawatt output).

Assuming the most expensive nuclear power plant in the world, assuming the solar is free and you are only paying for the batteries, assuming costs in line with the cheapest grid-scale battery storage in the world, about 6.5h worth of that nuclear plant's output.

That's on the right scale to power California with renewables alone! That's within sight. Anywhere less sunny, powering things with solar and batteries alone would still be very expensive.

Well, how much is it? Nuclear costs are front loaded.

Nuclear isn't the enemy here.

I can build a capacitor bank in my garage that produces more power than a nuclear power plant. For a millisecond.

Not when you are talking about compensating for short term peaks. Of course the amount of time it can do this is also important but, unlike batteries used for shifting solar energy to night time use for instance, it is not the most important feature.