Advertisements for tankless water heaters promise big savings. But are they accurate?
Unlike a traditional water heater, a tankless model does not store hot water. It heats water only as it’s used. Heating elements within the heater are activated when a hot water faucet is opened.
Makers of tankless water heaters generally cite four advantages over a tank-type heater: unlimited, continuous supply of hot water; instantaneous hot water; reduced water-heating costs; and small amount of space required.
It is true that tankless heaters do not require much space. But even the largest whole-house tankless unit may not supply enough hot water for simultaneous, multiple uses. Such a unit may be able to supply only two showers simultaneously or perhaps one shower, a dishwasher, and a sink.
Water temperature rise will be determined by the kilowatt capacity of the heating unit, the water flow, and the temperature of the incoming water. As the incoming water temperature drops, or as the volume of water moving through the heater increases, the water temperature will decrease.
Tankless water heaters usually require an expensive upgrade in electrical service.
—NRECA Cooperative Research Network