California’s Power Shift: Solar Generation Doubles in Five Years as Natural Gas Output Declines Amid Peak-Day Battery Storage Gains
Source：solarquarter
California’s electricity generation landscape is shifting, with solar power increasingly taking the lead while reliance on natural gas continues to decline, according to the latest data from the U.S. Energy Information Administration (EIA) and the California Independent System Operator (CAISO).
From January through August 2025, California generated 140.9 billion kilowatthours (BkWh) of electricity, marking an 8% increase compared with the same period in 2020. The growth has been largely driven by solar energy. Utility-scale solar plants produced 40.3 BkWh in the first eight months of 2025—nearly double the 22.0 BkWh recorded in 2020—and up 17% from 2024, adding 5.9 BkWh.
Conversely, electricity generation from natural gas fell sharply. Between January and August 2025, natural gas supplied 45.5 BkWh, 18% lower than in 2020. While output had temporarily increased in 2021 due to low hydroelectric output during drought conditions, natural gas generation has steadily declined since, with 2025 seeing a 17% year-over-year drop (9.5 BkWh) compared with 2024.
Seasonal trends highlight the complementarity between solar and natural gas. Midday natural gas generation decreases when solar output peaks. In May and June 2025, midday solar generation (noon to 5 p.m.) climbed to 18.8 gigawatts (GW) from 10.2 GW in 2020, according to CAISO. Meanwhile, excess solar energy stored in batteries has begun to offset evening natural gas use, with battery generation increasing from less than 1 GW in 2022 to 4.9 GW in 2025 during peak hours (5 p.m.–9 p.m.).
Experts note that natural gas remains critical during low-water years when hydroelectric output drops. For instance, in the first eight months of 2021, hydro generation fell to 10.3 BkWh, prompting natural gas output to spike to 63.5 BkWh.
CAISO revised its data collection methodology for natural gas in December 2023, making historical comparisons prior to 2023 non-comparable.
The data underscore California’s ongoing transition toward renewable energy, with solar and battery storage increasingly displacing natural gas, especially during peak daylight hours.