Heat pump water heaters use a motor to run a compressor.
The compressor draws a gaseous refrigerant through an evaporator, raising its pressure until it liquefies in the condenser. This familiar process heats the condenser and cools the evaporator. In wringing the heat from air, HPWHs both cool and dehumidify the air that passes through them, thus helping to meet space conditioning needs during cooling seasons. Under most scenarios, the extra costs of heat pump water heaters over standard electric water heaters are paid back in two to three years. HPWH systems are available in the U.S. in a variety of capacities, from small residential to large commercial, producing more than 350 gallons per hour of hot water and 6 tons of air conditioning.