58MTB Performance Efficiency Up to 93% AFUE Warranty 5-year limited parts 20-year warranty on "Super STM" heat exchanger Energy Star® Details As an Energy Star partner, Carrier Corporation has determined that the PerformanceTM 93 gas furnace meets the Energy Star guidelines for energy efficiency. Controls Controls Supported Thermidistat, Thermostat Diagnostics On Board Technology Capacity 38,000 - 128,000 BTUH Blower Motor Two-stage Primary Heat Exchanger SerpentuffTM polypropylene-coated Fuel Natural Gas; convertible to liquid propane (LP) Aesthetics Profile 2 Stage Multipoise Construction Galvanized steel Paint Baked on urethane base coat and polyester top coat