KD Navien® NPE-150S2 NPE-S2 Series High Efficiency Premium Standard Tankless Gas Water Heater, Natural Gas/Liquid Propane Fuel, 18000 to 120000 Btu/hr Heating, Indoor/Outdoor: Indoor/Outdoor, Condensing, 6.8 gpm at 35 deg F Flow Rate, 2 in Vent, Dual