At Stiebel Eltron, our goal is to provide energy efficiency in addition to comfort. Our heat pump water heaters are designed from the ground up to rely on the heat pump, not on the back-up element because that is the most efficient way. Our “50-gallon” heat pump water heater is actually 58 gallons and our 80-gallon model is, well, 80 gallons, because large is the best for a heat pump water heater. Large capacity means the water you are using, as much as possible, was heated the most efficient way — with the heat pump. We super-insulate our tanks, because minimizing stand-by losses means less energy is wasted. For maximum energy savings it makes no sense to skimp on the insulation and increase energy consumption. We use a single resistance element for back-up water heating during times of high demand. Our single booster element is located in the most efficient place — at the very top of the tank because that’s where the hot water is drawn from.