I replaced my natural gas water tank with a hybrid water tank. It has a built-in heat pump in the top of it. Not only does it use less power than a normal electric tank, but I'm able to do tricky things with the air flow of the water heater. I duct into the air intake warm air from the attic so that the water heater's heat pump doesn't have to work as hard to find heat in the air it draws in. As far as the free cold air the water heater produces, I dump that into the floor next to the water heater where a new HVAC receiver pulls that free cold air into the home HVAC ducts so that my home heat pump doesn't have to work as hard in the warm months making cold air. (In the winter I duct the water heater's cold air output into the attic.) That fact that the variable speed heat pump runs almost constantly (even at slow speed) means that there's never a moment when the water heater is spitting out free cold air that my HVAC won't pick it up to use that free cold air. (The house as a whole is more efficient than the sum of its parts.)
When you think about little stuff like that it's, duh!! How did I not do that years ago! Free heat energy in the attic -- might as well use that to help heat the water tank. Get a water tank that makes free cold air for 2-3 hours per day so you can use that to help cool the home. Even if I had never gone solar I should have thought about simple efficiency improvements like that. When I did the math and analysis to figure out if and how I could cost effectively take in and store solar power, it was only at that point I also began to study how I could more efficiently use the energy once it's in the home. Half of the battle won in making my solar produce 80% of all the power I need in my home is won by the fact that my home no longer needs a lot of power anyway. I still grumble a lot about the Dims' stupid war on energy. But I point one finger at myself for not doing what I could on my end until 2 years ago.
Guys reading your post are going to lust for that setup, very nice.