That might have to do with existing deal structures to maintain a non-renewable base load. Something like, if cloud cover/wind suddenly changes, we want to ensure there is already X% of natural gas running so there is a less sudden surge. There is a lot behind the scenes planning to try and ensure grid robustness.

California is certainly curtailing a lot of energy. EIA report[0] said 3.4 TWh in 2024, which was a 29% increase over 2023. If I am reading this[1] chart correctly, the 2024 California demand was ~275TWh.

CASIO also has pages dedicated to curtailment with much of the data available[2].

[0] https://www.eia.gov/todayinenergy/detail.php?id=65364

[1] PDF https://www.energy.ca.gov/sites/default/files/2024-11/2024_C...

[2] https://www.caiso.com/about/our-business/managing-the-evolvi...