I found this article helpful: https://www.manhattancontrarian.com/blog/2020-8-16-h7249j4l4...

From that article:

    Take out all of the solar and wind capacity, and California has
    only about 43 GW of capacity to meet demand that could well
    exceed that on any hot summer day.  And to get to that 43 GW,
    you would need all other facilities up and running at absolutely
    full capacity with no scheduled or unscheduled outages, which
    is not realistic.  Yes, you could try to import some power from
    the neighboring states, but at times of peak usage they probably
    need all of their own power.  In short, you have put yourself
    in a position where regular intentional blackouts are inevitable.
    And, as more and more reliable fossil fuel and nuclear facilities
    get closed in favor of wind and solar, the problem looks set
    to worsen dramatically over the next several years