Domestic hot water heat pumps are a type of hot water heating system that uses electricity to move heat from one place to another, rather than generating heat directly. As a result, they are typically two to three times more energy efficient than traditional electric resistance water heaters. Domestic hot water heat pumps work in a similar way to a refrigerator which works in reverse; whereas a refrigerator extracts heat from an enclosed space and releases it into the surrounding air, a domestic hot water heat pump extracts heat from the surrounding air and transfers it to a closed tank to heat the water.