Without any experience doing it, I installed a solar system to run the fish heaters, pumps and whatever in the backyard back in January 10,000 amp hours of batteries, 48 volt system but only a 3500 watt inverter with two charge controllers, powered by 18 200 watt panels, with about a 25% efficiency rating, used military surplus for $60 a piece.

I haven't used solar power to heat the water in months, the air temperature does that, the water almost got to hot a few times, and I don't have a water cooler, but not hot enough to be in the life threatening range.