I live in St. Augustine and my Aquacal Icebreaker not only kept my pool (6600gal fiberglass) warm all winer it will heat my spa (300 gal acrylic) to 100 deg. in abut 15 mintues! Heatpumps cost more inially but if you look at the cost over a 10 year period vs electric or gas they will actually save you money.(at least in Fl)