This 6.4 GPM 199,000 BTU Natural Gas Tankless Water Heater is Energy Star qualified and can help you save on utility bills. It has an automatic shutoff and operates only when needed to help minimize energy loss. This heater features dual stainless-steel heat exchangers and a 3-phase, pre-mixed burner to provide hot water reliably when needed. A built-in leak detector is included to provide peace of mind and enhance this heater's efficiency. Also includes Circulation Pump with Mini Buffer Tank minimizing hot/cold/hot stacking, the so called Cold Water Sandwich.