California wind and solar projects were ordered to cut back electricity deliveries by a little under 4% in 2020, or 1.6 million megawatt hours.

Such curtailments are expected to increase over time, potentially complicating financings of future projects.

Curtailments increased 66% compared to 2019 and 246% compared to 2018. Most curtailments are at mid-day during periods of peak solar output. They reached 7% in April 2020 when stay-at-home orders were in effect and many businesses were shut down.

The California grid operator expects renewable energy generators to face curtailments of 7% to 17% by 2030 based on the current resource mix projected by the California Public Utilities Commission. Installation of large batteries that shift electricity deliveries to other times of day and mass electrification of the transportation sector could help. Less predictable revenues become a factor in how much financing can be raised on projects.