KD Navien® NPE-180A2 NPE-A2 Series High Efficiency Premium Advanced Tankless Gas Water Heater, Natural Gas/Liquid Propane Fuel, 10000 to 150000 Btu/hr Heating, Indoor/Outdoor: Indoor/Outdoor, Condensing, 8.4 gpm at 35 deg F Flow Rate, 2 in Vent, Dual