AFUE
Annual Fuel Utilization Efficiency — the percentage of fuel a furnace turns into usable heat over a season. An 80% AFUE furnace sends roughly 20% of the fuel's energy up the flue; a 96% unit sends 4%. The gap matters most on expensive fuel like propane.
Parts behind the term
Whatever this term touches, it's on a shelf in Asheville with same-day pickup.