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AFUE rating
AFUE stands for Annual Fuel Utilization Efficiency and measures how efficiently a furnace or boiler converts fuel to heat.
Why it matters
Higher AFUE means less fuel is wasted. Modern high-efficiency furnaces can be 95% or higher, compared to 80% or less for older units.
Where people get this wrong
AFUE measures the equipment only, not the duct system. A 96% furnace connected to leaky ducts still wastes energy.
Real-world example
An old furnace has an 80% AFUE. A new one is 96%. That means 16 cents of every fuel dollar that used to go up the flue now heats the home.
Where this hits your build
This affects daily comfort in every room. Problems often show up after move-in when certain rooms run hot, cold, or noisy.
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