AFUE Rating
Updated
AFUE stands for Annual Fuel Utilization Efficiency, and it tells you what percentage of the fuel a furnace burns actually becomes heat in your home.
An 80 AFUE furnace turns 80% of its gas into usable heat and sends the rest up the flue; a 95+ AFUE condensing furnace captures most of that escaping heat before it leaves. Think of it as the heating-fuel cousin of a SEER rating. Higher-AFUE equipment costs more up front and pulls enough extra heat from the exhaust that it produces condensate, which has to drain somewhere. Whether the upgrade pays off depends on how long you plan to stay and what you pay for gas.
Common Questions
What does AFUE measure?
AFUE measures how much of the fuel a gas furnace burns ends up as heat inside your house instead of going up the flue. It is expressed as a percentage, so an 80 AFUE furnace delivers 80 cents of heat for every fuel dollar.
Why do high-efficiency furnaces have a drain line?
Condensing furnaces pull so much heat out of the exhaust that water vapor in it condenses back to liquid, and that water needs a path out. A floor drain handles it when one is nearby; otherwise a condensate pump moves it to wherever the drain actually is.
Is a 95+ AFUE furnace worth the extra cost?
The math depends on your gas rates and how long you will own the home, so it deserves real numbers rather than a rule of thumb. A furnace installation quote laying out both options side by side is how that decision actually gets made.
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