Efficiency ratings
AFUE
Annual Fuel Utilization Efficiency — how much of the fuel a gas furnace converts to usable heat over a year.
AFUE expresses gas-furnace efficiency as a percentage. An 80% AFUE furnace converts 80¢ of every $1 of gas to heat — the rest goes up the flue. New high-efficiency condensing furnaces hit 96–98% AFUE, the legal minimum in Canada is 90%.
In 2026, mid-efficiency (80%) furnaces are no longer manufactured for residential use here. If you still own one, you're spending roughly $1 of every $5 on gas you'll never feel. A typical Mississauga home replacing an 80% with a 96% saves $300–$500/year on heating gas.
AFUE is a steady-state lab rating. Real-world efficiency depends on sizing, ductwork, and runtime patterns — which is why we do a Manual J before quoting a replacement.
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