We just recently installed a gas heater. I teach swim lessons to infants and toddlers in the evenings and the ideal temp is 90. So, I'm wondering if it is more cost efficient to leave the heater running or turn it off every day and make it work harder to get to 90. We are in Texas so right now its still in the 90s every day so the pool is not losing much heat. But what about when it does get cooler?