Amana offers gas furnaces from 80% AFUE all the way to 96% AFUE for Amanas top of the line gas furnaces. In their gas furnaces Amana offers their patented Million AirTM stainless-steel tubular heat exchanger which they have tested under extreme temperature conditions for durability. That can give you peace of mind for safety and longevity reasons for the gas furnace heat exchanger. Amana also offers variable speed blowers in their top of the line to mid range gas furnaces. Amana offers good parts only warranties on their furnaces. Some are lifetime warranties (terms and conditions apply). The higher efficiency models use variable speed blowers for added efficiency and state of the art electronics for ignition and diagnostics.