During the winter the compressor heats the tank during the utility off-peak hours. This is because the HPWH gets heat from the air in the room. As a side benefit, a HPWH also dehumidifies and cools the air. In a way, a HPWH is similar to a heat pump desuperheater coil. The main difference is that a HPWH provides hot water directly by using a very small compressor either mounted on the tank or situated nearby.
Many manufacturers also have adapter kits for retrofiting existing water heater tanks.
Integrated Ventilation Systems Indoor air quality is of particular concern to residents of airtight, energy-efficient houses. Such designs also often have electric resistance heating elements to add additional heat during times of large hot water use. Water Heating A tankless coil for domestic water heating with a hydronic or steam boiler has been available for about 100 years. The domestic hot water coil is a heat exchanger inside the boiler that absorbs the boiler s heat in order to make domestic water. It does not have any significant storage abilities so owners of such devices often complain about running out of hot water at critical times.