Designed to replace a 40 gallon storage tank, Over 90% efficiency rating, Provides an endless supply of hot water, Solid copper heat exchanger, No temperature/pressure relief valve necessary (check local codes), External temperature control knob, Saves space, saves energy, Thermal cut-out for safety, Not recommended in climates where annual ground water temperature is less than 60F, Watts: 17, 25 KW, Volts: 240V, SKU: HMREX1147