Propane and natural gas have the highest operating cost, and are the least efficient / cost effective way to heat a pool, but if you require rapid heat up, constant temperature regardless of outside temperature, or you are heating a spa or hot tub, then a gas heater may be right for you. See alternative heating options to be sure Gas Heating is the right choice for you: Side-by-Side Comparison Guide To purchase a Gas Pool Heater please visit: Solar Direct's The Energy SuperMarket