Comment sparks, not capacity, seemed to be the issue (Score 1) 80
I'm not sure, but my experiences with rolling blackouts in northern CA haven't been about grid capacity in the last 15 or so years.
All the rolling blackouts I've seen were to prevent fires from above-ground power lines, which caused massive fires, death and destructive when conditions were dry and winds were high.
High winds and dry vegetion + above ground power lines = rolling blackout.
Power plant batteries would have nothing to do with such rolling blackouts.
Other parts of the country, e.g., Texas, seem to have rolling blackouts because of dificient capacity at times.