Washroom water heaters typically come in two varieties: storage water heaters and tankless water heaters. Storage water heaters store and repeatedly heat water within a tank, while tankless water heaters instantly heat water as it flows through the device, and do not retain any water internally except for what is in the heat exchanger coil. They are typically used to provide heated water for sinks and shower heads.
With traditional storage water heaters, once the water stored inside the tank has been heated, it may be streamed until it is depleted, at which point the new supply of water must be heated. Washroom water heaters tend to have a smaller tank than a typical boiler.
Tankless water heaters are typically installed near their point of use. Unlike storage water heaters, these devices offer a plentiful continuous flow of hot water and potential energy savings thanks to their greater efficiency.
Certain models of washroom water heaters are intended to be installed in specific locations, such as under sinks. Many, but not all, feature a component for temperature control such as a knob.