Californian batteries set new output record

As the solar and energy storage industries brace for shifting political winds in Washington D.C., California continues to do what it does best: break clean energy records.

At 7:45 p.m. on May 20, battery systems connected to the California Independent System Operator (CAISO) grid hit a new peak instantaneous electricity output of 10,030 MW, becoming the single largest source of electricity on the grid at that moment and the second highest peak output of the day, behind solar power generation.

On the following day, CAISO set a new renewables generation record of 28,242 MW, at 1:05 p.m., even as demand hovered near just 21 GW. The resulting surplus would have been unmanageable without California’s expanded battery fleet, which continues to absorb midday solar power generation and prevent widespread curtailment of excess electricity.

The largest battery charging period occurred between 10:00 a.m. and 11:00 a.m., with roughly 6.9 GW of instantaneous solar-sourced electricity stored.

That record-setting battery output was driven by significant new capacity additions. According to regulator the California Energy Commission (CEC), as of April, the state reached 15,763 MW of battery capacity.

This value has increased from just over 13 GW, reported in fall 2024. The CEC expects another 8.6 GW of capacity to come online over the next two years.

Daniel Snowden-Ifft, a physicist at Occidental College, and regular reader of pv magazine USA, said the CEC figures showed the energy storage deployment rate “a little low but still basically on track” for California to reach its 52 GW target well before 2045.

The CEC reports 252,889 energy storage installations across the state. Of these, 214 are utility-scale facilities, representing less than 0.01% of installations but accounting for 84% of total capacity, with an average output of 62 MW each. In contrast, residential systems number 249,340 and total 1,829 MW of capacity, making up 98.5% of installations and 11.6% of deployed capacity.

The Sunshine State also set new benchmarks for solar generation.

On May 22, at 12:35 p.m. local time, CAISO recorded a new all-time high for utility-scale solar generation: 21,556 MW of instantaneous output. The new record edged out the previous day’s by 35 MW, and marked the fourth time in 2025 that a new solar generation peak has been set.

As shown in the chart above from GridStatus.io, solar generation records are typically set during the spring, although 2024’s record peak occurred in August. Following California’s solar surge, with output up 33.8% early in the year, the state’s spring solar peak has already climbed nearly 10% versus 2024.

Notably, the 21.6 GW figure includes only utility-scale solar. California also hosts nearly 20 GW of distributed solar across rooftops and businesses, bringing the state’s combined peak solar generation output to more than 40 GW. Over the past 12 months, solar has supplied close to 34% of the state’s total electricity generation.

From pv magazine USA.