I’m taking a course on power generation, transmission, and distribution, and you basically said what I wanted to say.

If you look at generation in California, there’s a huge peak during the day (due to the increased supply of power from solar) and a decreased demand for power in general (because needs are being met by individual solar). The extra power needs to be stored/used or wasted. No other options, which is what makes solar weaker (than it could be) right now - we don’t have the storage capacity to be keeping the excess for nighttime.