@ifixcoinops I'm not sure the water heater has enough thermal mass to make a difference. Thirty-plus years ago my father replaced the AC in his South Florida home with one that had an energy saving feature: it could leverage the pool water to dump heat. It would circulate the water out of the pool then back in, warmer.

This is not a lap pool but not small either.

He ended up having to create a bypass for it because the pool started to exceed 100F. And that's thousands of gallons, not tens.