Don't know about you, but we run a saltwater system in our pool, so having metal involved in the scenario is a bad idea. Okay, I have no great pictures, but here is a shot when the pool and yard was just going in. We are on 1 acre so have plenty of room for lots of stuff. Our solar is up behind the pool on the upper level, south facing. We have a controller, but invariably when you kick it on, the water in the pipes under the ground have stored cold water in them. Also, my wife WONT get in the pool unless it is 91 or warmer, so we tend to keep it quite warm. Again, I am not saying you can't accomplish what you want, but to do it right is very expensive and PERSONALLY, it is not a payback.
Personally, I love to tinker with stuff like this as I am kind of one of those doomsday nuts who would like to be totally self sufficient! We have a big garden, orchard, greenhouse, chickens etc for food, and I have a 5000 gal buried propane tank that runs a back-up generator for this house just in case. I also have a wood burning fireplace that is plumbed so that I can heat the entire house with it if I need to.....I think you see where I am going with this. My whole point was, do it if you dig that kind of stuff, but don't do it as a cost effective way to pay it back. The original cost of the system will significantly outweigh the cost of buying gas (this is my opinion based on my personal experience) Now would I go and do it again? Probably, just because I love this kind of stuff! Now a heat pump will probably be my next adventure, I just need to find someone who can dig me some deep holes!