patrick.net

There are good use cases for solar, but I doubt that solar cells are one of those cases.

Using a parabolic mirror to concentrate sunlight on the cold water input to a hot water tank sounds cost-effective.

Arranging houses to take advantage of sunlight via solar mass is an old method that works. Iranians had that worked out millenia ago. They also did clever cooling with solar-heated chimneys.

I've long thought that algae and yeast based solar cells to create and then ferment sugars into burnable alcohol might also be worthwhile.

Patrick says

Using a parabolic mirror to concentrate sunlight on the cold water input to a hot water tank sounds cost-effective.

That is a common technique out here. Virgina law requires that a rooftop solar water heater must feed into a conventional hot water tank. The purpose is to cool down the water since the rooftop system will heat the water above the 160 degrees considered safe for a hot water supply. I had an Australian friend tell me that back home there is no water heaters, as the issue there is cooling the water down (Australia is partly in the tropics).