My oldest boy just moved into a new home with his wife and it has an in ground pool with a solar heater on the roof, Doesn't get alot of sun though as the trees on the property are 40-50 yr old Oak, Maples and Ash so we have been messing with the setting to maximize the heat then dump it in the pool, Hes going to need a solar blanket for night time though to hold in the heat, It was 75°F in the pool last friday when they moved in and now its 67°F.