
Why don't I see these everywhere? I had a solar hot water system in my previous house outside of Gainesville. It was designed and installed by me!! I would estimate it was hot from the sun 98% of the days and the temp was superhot most of the time. You have to install a mixing valve to mix cold water with it to keep it from coming out burning hot.
Here is a link about solar hot water.
I currently do have a solar pool heater as my pool is mostly in the shade of big oaks..