Solar with Battery storage is a very useful source for heating energy, even in the coldest climates in CA. Even in the mountains where it drops below freezing at night, most places it's still sunny a lot more than the US average during the day. Most Battery setups I know of target a 4 day stretch of cloud cover for storage capacity, so it is certainly an option.

Where I live at 7000 feet, we have so much sunshine, even in winter, solar is a very viable option. Legislation removing people's ability to recoup the costs is the only reason it's not in every house in the city. The only option left is a much more costly battery setup.

California (and everywhere else) could make solar a lot more useful by making electricity cheaper from 10am to 3pm. If heat pumps and electric water heaters were set up to run more when the sun is out, it would noticeably decrease the evening spike in electricity demand.

Solar takes demand out of the entire pie. So less natural gas needed during peak hours. Also move some of that excess in to energy storage and you can cover during that time in the morning.

Nonsense. You can put excess energy into large electric hot water heater tanks and use it later.

It requires a minimal amount of "smarts" and is all standard plumbing.