Heat pump water heater uses small amount of electricity to move heat from the surrounding air to the water and therefore can deliver hot water up to 2-1/2 times as efficiently as common electric resistance water heater although saving will vary depending on your climate zone prices of your electricity and family hot water demands saving per year 4 family between $400 and $70 and family of 6 can save between $80 and $570 per year.with saving like that it is not common like that to pay for themselves in 3-4 years and continue to save energy and money used after that

Heat pump water heater works by moving heat from the air in the room to water in the tank
the heat in the air observer by a vapor refrigerator flowing through the
evaporator.