The Vertex™ 75-Gallon Ultra-Low NOx Power Direct Vent Natural Gas Water Heater offers unprecedented levels of performance to meet your hot water needs. Featuring a 75-gallon (nominal) tank and an AiQ - Adaptive Gas Technology allows you to select Natural Gas or Liquid Propane during installation, the HDHE-75 400 series Power Direct Vent delivers a thermal efficiency of 96%, a Uniform Energy Factor of 0.86, and a recovery rate of 150 gallons per hour. It carries a 8-year limited warranty, and meets Ultra-Low NOx emission requirements. Environmentally-friendly insulation and factory-installed heat trap nipples reduce heat loss for maximum energy savings. This Vertex™ water heater is designed with A. O. Smith's superior commercial-grade tank protection. Advanced tank features include stainless steel CoreGard™ anode rod, Blue Diamond® glass lining and DynaClean™ automatic sediment-cleaning system, all designed to help protect the tank from the corrosive effects of water and extend the life of the water heater. A. O. Smith’s ProLine® water heaters are residential products built to commercial-grade standards and are only available for purchase through professional wholesalers and contractors.