We live in SW Florida and we have a 15K gallon 15' x 30' AG pool with 2' sub grade leaving about 18" of water above grade. We just installed a gas heater and now wonder about best operating practices...we have a solar cover installed when we're not in the pool...question I'm asking myself now is do you leave the heater off until you anticipate using it or do you heat it a bit all time time and heat it to the desired temp just prior to use? I'd imagine someone has done the math and I realize it's ambient temperature dependent...