Analysis by CEC Economics
Highlight
- Although curtailment has been increasing, it makes up a small percentage of total in-state generation. In 2023, in-state generation from solar was 41,344 GWh; the curtailment represented 6.1% of in-state generation. Wind curtailment was 1.1% of in-state generation in 2023. Also, electricity generated from renewable sources tend to be higher when curtailment is also high.
Challenges
- In California, curtailments83 have been rising every year, driven by growth in solar power to meet the state’s ambitious clean energy goals. As more renewables come online, without robust additional transmission and storage buildout, California faces an increasing amount of wind and solar generation curtailment, especially during the middle of the day (from 10 AM to 2 PM), when there is an oversupply of solar.
- In the first nine months of 2024, curtailment totaled 3,102 GWh electricity generated (210 GWh from wind and 2,892 GWh from solar), which has already surpassed the total curtailment of 2,660 GWh in 2023. This 9-month curtailment in 2024 represents a 32.4% increase from the first nine months of 2023 (2,343 GWh), which itself is more than 3.5 times of the total curtailment amount in 2018 (461.0 GWh). Wind and solar curtailments rose by 51.1% and 31.2%, respectively, during the first nine months of 2024 relative to the first nine months of 2023.
83 Curtailment is the reduction of output of a renewable resource below what it could have otherwise produced. At times power generators may produce output that is not needed. In the absence of energy storage systems, the surplus may have to be dumped, or the power plant output turned down or switched off for a while.
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