Batteries are taking on gas plants to power California’s nights

California spent the last decade building up a massive fleet of batteries to help clean up its electrical grid. This spring, those storage plants passed a major threshold, and now are visibly reshaping the state’s power grid — just as clean energy advocates said they would.

Governor Gavin Newsom announced in late April that California hit the 10 gigawatt mark for installed battery capacity, well beyond what any other states — or entire countries — have achieved. That’s about 13 times more battery capacity than the state had installed just five years ago, and it’s enough to make batteries a meaningful portion of the state’s power supply. For reference, 10 gigawatts are enough to meet about 20 percent of the peak electricity demand recorded in the grid managed by the California Independent System Operator (CAISO).

With this kind of scale, it’s possible to investigate if batteries are doing the tasks that their fans have long promised: manage the evening decline of solar, enable more solar generation, and reduce the need to burn fossil gas.

The newest real-world data from April suggest all those things are now happening.

It’s important to note that shoulder months like April are favorable to California’s clean energy system: Mild weather means lower electricity demand from air conditioning, so it’s easier for solar to meet customers’ needs. But the sun still sets in the springtime, so there are hours when gas and batteries compete to fill in the gaps.

Data analysis firm Grid Status compiled a series of illuminating charts showing how the grid has changed as more batteries have materialized. Take the average 24-hour operations of the CAISO battery fleet. Just six years ago, the scale of battery charging and discharging was so minimal that it barely registers on the graph. As time goes on, the lines steepen: The batteries charge far more during the sunny hours, when solar generation is cheap and abundant; they release far more power back to the grid in the evening, when the solar production fades out, and in the morning, before it resumes.

Strikingly, in the last year alone the average April evening battery discharge fully doubled, to 5 gigawatts. But given that California now has 10 gigawatts of batteries installed (some of which fall outside the CAISO boundaries), that means there’s already room to drastically expand that performance.

The recent battery surge coincides with a breakthrough in California solar production. Solar power has to be used when it’s generated, or stored for later. But California’s solar fleet got started well ahead of the battery buildout, and the state found itself with so much production at midday that it had to throw away gigawatts of cheap clean power for lack of a place to send them.

Grid Status plotted solar generation over the last six years and found that April production stalled out around 9 gigawatts during 2018, 2019, and 2020. Then it jumped up to a higher level from 2021 to 2023, approaching 12 gigawatts. In 2024, this shot up to a new higher quantum, touching 15 gigawatts.

Many factors could explain this — for one thing, California added a record 6 gigawatts of solar last year. But it’s clear that storage plays a significant role, as evidenced in the first chart, depicting batteries loading up on that midday energy. The glut of midday solar depresses prices and makes it effectively impossible to finance new stand-alone solar plants to compete in that saturated market. Adding storage makes the economics work out for new solar projects by shifting a chunk of their output to more valuable evening times.

That leaves gas, which remains the backbone of California’s power system despite the state’s nation-leading push toward clean energy. All the new solar only made gas more vital to rapidly respond to the rising power needs in the evening, as popularized in the infamous duck curve. But something striking happened this April, compared with Aprils past: The evening gas surge crumpled.

For the past three Aprils, the CAISO gas fleet has fired up after sundown, pumping 9 to 10 gigawatts onto the system as solar generation disappears. In April 2024, gas only got up to a bit more than 5 gigawatts. The chart shows a gas fleet that yearns to reach the heights it regularly hit in years past, but instead is bumping into some new force that halts its rise.

Guess what that force blocking the gas fleet might be?

Dispatch data from CAISO shows that the evening hours are now a hotbed for battery activity. For instance, on the last day of April, the battery fleet kicked in around 6 p.m. and ran through midnight. The batteries hit a record for most power delivered just before 8 p.m., with 7 gigawatts; that was within spitting distance of the gas fleet’s performance at the time, something unheard of in years past.

For years, evenings in California were fossil gas’s time to shine. Now the evening capacity role is increasingly a toss-up with batteries, at least in the shoulder months. Gas will still play a crucial role in the hotter months as evening demand outstrips the capacity of the shiny new battery fleet. But the trends in April are validating the thesis that storage plus solar can extend the clean energy transition into the nighttime — and California’s clean energy fleet is only getting bigger.