Heat pumps are super-efficient and when sized properly, and used regularly, they can literally pay for themselves. When there is a pool/spa combo we believe a gas fired heater is essential for the rapid heat rise (speed to heat up the spa). When there is a “pool only” and one is going to want to heat the pool regularly, a heat pump is the logical alternative. Heat pumps work slowly and efficiently. They are a “set-it-and-forget-it” way of heating the pool.