Designed to provide an endless supply of hot water for kitchen, bathroom, and handwashing sinks. 99% efficient. 5 year warranty on heater, 1 year on parts for both commercial and residential use. Installs vertically or horizontally. Solid copper heat exchanger, copper-sheathed elements, and tough plastic housing. No temperature/pressure relief valve necessary (check local codes). Has thermostatic adjustable control. Unit must be hard wired.