Featuring the same energy-saving condensing technology as the rest of the Noritz ecoTOUGH Series of gas-fired residential tankless water heaters, the NRC661 has an energy factor of 0.91 for natural gas and 0.93 for LP. This small-scale water heater can deliver 6.6 gpm, with a maximum input of 120,000 Btu, using a 1/2” gas line up to 120’ length. Other features include a built-in digital display, low minimum input and an accessible technical data sheet.