Furnace Comparisons-2200 Hrs. Or Heating Per Year 80% Efficient Singles State Furnace * Warmer Heat Coming Out Of The Registers 115-120F * Less Efficient At 80% * Uses More Gas And Costs More To Operate - Gas Useage * 20 Year Heat Exchanger Warranty And 5 Year Part 80% 2 Stage Furnace * Very Close To 90% Efficient Furnace With First Stage * First Stages Is 70% Gas Useage * Second Stage Is 100%...