If your current water heater uses electric resistance elements to heat the hot water, or if you have a water heater that runs off of propane or fuel oil, you should consider installing an air source heat pump water heater. They use electricity to move heat from the surrounding air into your water heater tank. Because the technology moves heat rather than generating heat, heat pump water heaters are often 2-3 times more efficient than electric resistance water heaters and are also much cheaper to operate than fuel oil and propane water heaters.