Hot Water and Cool Air
heat-pump water heaters are very efficient because they transfer heat rather than creating it.
In an all-electric house, a heat-pump water heater (HPWH) is the natural choice. Just like air conditioners, HPWHs rely on refrigerant phase changes to transfer heat from the surrounding air to the water in the tank. The by-product is cooler, less humid air. Because they transfer heat rather than creating heat, these water heaters are very efficient, with energy factors as high as 3.39—effectively producing $3.39 worth of energy from $1 of electricity. To overcome the slow recovery rate, an electrical-resistance heating element can be used in place of the heat pump or to supplement it.