Natural gas tankless water heater, maximum 140,000 BTU (British thermal unit) for 1 major appliance or 1 shower at a time. ENERGY STAR qualified. Scale reduction software, freeze protection, and multiple safety features. Unit requires category 3 stainless steel piping. Must vent independently. Direct vent conversion kits available. For vent kit refer to model No. 9008001 (SKU 400474). Energy factor: 0.82. 12 year limited warranty on heat exchanger. 5 year limited warranty on parts. Unit dimensions: 13.80" W x 6.70" D x 20.50" H.