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.
California has done so well with clean energy resources, that in 2024, California Independent System Operator (California ISO) clean energy supply equaled or exceeded demand in the California ISO service area for nearly 1,227 hours over 219 different days*. That’s equivalent to 51 days of meeting demand with 100 percent clean electricity.
What’s more, the numbers are trending even higher for 2025. In just the first quarter of this year, the California ISO clean energy supply equaled or exceeded demand in its service area for nearly 468 hours over 77 different days. That’s the equivalent of almost 20 days of meeting demand with 100 percent clean electricity. Projected out over a full year, that would be almost 80 days, potentially more than a 50 percent increase over the previous year.
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 |
| 1/1/2025 to 5/31/2025 | 12,002 | 1,000.17 | 41.7 | 192% | 11.3 | 138 |
*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.