The mix of energy sources used for power generation in California this summer changed from last summer, as renewables and imported electricity offset lower natural gas use. During summer 2016 (June, July, and August), thermal generation (almost all from natural gas) in the area serviced by the California Independent System Operator (CAISO) was down 20% from the previous summer, while generation from hydroelectricity, other renewables, and electricity imports was higher than the same period last year. The overall level of electricity consumption was 2% higher this summer as temperatures were slightly warmer than the previous summer.

Hydroelectric generation in CAISO increased from last summer because the West Coast drought situation has improved. According to the U.S. Drought Monitor, 59% of California experienced a severe, extreme, or exceptional drought during July 2016. In contrast, 95% of the state experienced similar conditions last July. These improved water conditions have also helped increase hydroelectric generation in the Pacific Northwest, some of which is imported into CAISO.

The addition of new generating capacity has also contributed to the change in generation mix. Data from CAISO indicate that nonhydro renewables, mainly solar and wind, represented 26% of capacity in June 2016. Utility-scale solar photovoltaic (PV) capacity has shown the most growth in CAISO recently, increasing by 1.4 gigawatts (27%) between June 2015 and June 2016. This increase in utility-scale solar capacity has reduced the need for summer thermal generation in CAISO, especially during the daylight hours.

California also has added a significant amount of distributed solar PV capacity. EIA's latest data show that distributed solar PV increased from 2.8 gigawatts in June 2015 to 3.8 gigawatts in June 2016. Distributed generation reduces the amount of electricity that utility-scale power plants need to supply.