Features: Tankless design uses up to 199,000 BTUs per hour todeliver an endless supply of hot water Conveniently mounts to your wall Large 10 GPM flow rate and variable temperature controls Requires direct venting Meets SCAQMD 1146.2 requirements for Ultra-Low NOx regulations of less than 20ppm Suitable for 3 bath homes in northern climates and 4 bath homes in southern climates Designed for indoor use only Composed of commercial-grade materials for thebest durability Onboard computer modulates combustion to achieve an energy factor of .95 all while meeting strict gas emission standards Integrated recirculation pump allows for installation in homes with dedicated recirculation lines Designed to be installed indoors Specifications: Height: 23-3/5" Width: 17-3/4" Depth: 11-1/4" Vent Type: Direct Vent Duct Size: 3" or 4" Round Max BTU Input: 199,000 Fuel Type: Natural Gas Energy Factor: .95