This product has been designated as one of the Most Efficient Energy star qualified products in 2019. Products that are recognized as the Most Efficient of Energy star in 2019 prevent greenhouse gas emissions by meeting rigorous energy efficiency performance levels set by the U.S. Environmental Protection Agency;Fine-Tuned Fuel Use - The SL297NV operates at two different levels of heat output, so it maintains a consistent temperature in the home using as little fuel as possible;Stainless Steel Secondary Heat Exchanger - The secondary heat exchanger allows the furnace to achieve higher eifficiency levels by capturing additional heat;Smart Control - When combined with the iComfort S30 ultra smart thermsostat, the SL297NV adjusts the heating for energy savings based on the family's routine;Duel-Fuel-Capable - Can be combined with a Lennox electric heat pump for peak efficiency;Special Sound-Absorbing Insulation - Further reduces sounds for quiet operation;Warranty - 10 year limited warranty with product registration