Solar water heating was patented by a man in the North East. The February day the patent office was to view his invention was overcast and he asked for another day. They said "No, today is your day, it may be a year or more before we can come back". They came in, he started his pump and the water came back 20 degrees warmer than when he sent it out!
The only thing about solar is, you have to get used to wide temperature swings. But, you sure can't beat the energy cost.