California continues to lead the nation in bringing clean energy online. In addition, the state has invested heavily in battery energy storage, which captures power produced by wind and solar resources and discharges the energy back to the electric grid during times of peak demand.
In 2024, California achieved 100% clean energy in the California Independent System Operator (California ISO) service area for nearly three out of every five days (219 different days) for some period of the day. Over the course of the year, the California ISO system was powered by 100% clean energy for an average of 3.3 hours each days.
What’s more, the numbers are trending even higher for 2025. In just the first six months of this year, the California ISO reached 100% clean electricity for a portion of the day on 168 different days. In fact, the grid has been powered by 100% clean energy for an average of almost 7 hours each day.
Please note that the portion of daily demand exceeded by clean energy could be as short as 5 minutes. These examples demonstrate what is possible as the state transitions to a 100 percent clean energy future.
Also note that the California ISO serves about 80 percent of California’s electricity demand. Other California balancing authority service areas do not provide 5-minute updates, so a similar comparison is not currently available.
California Independent System Operator Clean Energy Calculations since 2022
| Year | Occurrences | Total Hours | Equivalent Days | Max Percent | Max Daily (hours) | Days When at Least One 5-minute Interval CE > Demand |
|---|---|---|---|---|---|---|
| 2022 | 1,764 | 147.00 | 6.1 | 126% | 9.4 | 43 |
| 2023 | 8,250 | 687.50 | 28.6 | 149% | 10.1 | 136 |
| 2024 | 14,721 | 1,226.75 | 51.1 | 175% | 11.1 | 219 |
| Through June 2025 | 14,949 | 1,245.75 | 51.9 | 192% | 11.3 | 168 |
*The CAISO evaluation of days served by clean energy uses California ISO published data presented on CAISO’s Today Outlook website which is provided for informational purposes only and should not be used for determining actual billing values, operational planning, or statewide progress in meeting California’s clean energy goals.
Clean energy sources counted include small hydro, solar, wind, biomass, geothermal, nuclear, and large hydro. The published California ISO demand evaluated does not include electricity consumed for pumping loads or to charge batteries and may not represent actual retail sales delivered to consumers. Renewables included from California ISO may not necessarily be certified for RPS compliance. In addition, the reported biomass supply may not reflect actual renewable generation as only the portion of the certified facility electricity generated from renewable feedstock would count as renewable electricity generation. California ISO’s Today’s Outlook data is subject to change without notice.