You know what else would make cooling your home energy efficient? If your home was not absorbing as much heat from the sun. Most roofs are black petroleum product, because oil everything! For not a whole lot of money, the cost of some digging, running pipes, and a pump, one could encase their home inside a closed loop 5mm tall waterfall during summer, which would drop their energy bill significantly. The idea is a little water runs over all outside surfaces of your home, taking whatever heat the surface of the home has with it (but also taking heat through evaporation) back down under the ground surface where it exchanges the heat. Add water as it is lost through evaporation. Really, if civil engineers and builders had made everything a water wonderland instead of heat absorbing black top, it would be a lot fn cooler.