The original theory was that the excess power from your solar array would power my air conditioning on sunny days. They wanted the power transfered to the grid so discouraged batteries. Now they are considering subsidizing them.
There are so many residential solar installations in California, that the ISO is getting worried about over generation. The graph describing the issue is called "The Duck Curve". This version shows that one solution is for solar homes to install batteries.
https://www.caiso.com/Documents/FlexibleResourcesHelpRenewables_FastFacts.pdf
My goal was to shut them up and embarrass their mother. Sex with the mother was good, but transitory. The children's behavior was always problematic.