I really don’t understand why solar hasn’t made better penetration in the domestic water heating market south of the Mason/Dixon line. Solar water and pool heating sounds like a “ no brainer “ to me.
I keep wondering why the AC industry hasn’t latched onto solar. By far my biggest electric cost (and that’s including an electric car!) is running the AC in summer. Since AC usage is closely related to amount of sunlight, best to cover the roof as you can with solar panels & siphon off some of that impinging energy, create a mechanical air gap to help blow away accumulating heat (via solar-powered fan), and use the gathered electricity to run the AC. Less sun = less electricity? no problem, you didn’t need that much for the AC under that condition. No buffering needed: run that equipment directly from the power as collected; again, as electricity produced reduces so does the demand. Insofar as direct powering may not be enough, at least you’re making a significant cut in grid use.
This as opposed to trying to run the minority of electricity use the most at low/no-sunlight periods, requiring more panels to inefficiently cache that with a bulky bank of expensive batteries.
The heaviest electrical load (at least in many regions) can be serviced with the simplest solar panel configuration: limited panel area, no batteries, specialized equipment with built-in cost-optimal alternate power input (to wit: no adapters into house power, only to get it mostly to that more cheaply capable of taking it directly).