KD Navien® NPE210S2 NPE-S2 Series High Efficiency Premium Standard Tankless Gas Water Heater, Natural Gas/Liquid Propane Fuel, 12000 to 180000 Btu/hr Heating, Indoor/Outdoor: Indoor/Outdoor, Condensing, 10.1 gpm at 35 deg F Flow Rate, 2 in Vent, Dual