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Understanding Your Furnace or Boilers AFUE Ratio

Monday, December 16, 2013

Furnaces and boilers on today’s market are required by the Federal Trade Commission to carry an Annual Fuel Utilization Efficiency ratio. It measures the amount of energy the furnace converts to heat compared to how much escapes through the chimney: the higher the number, the more efficient the furnace.

The AFUE is a key number in judging the efficiency of a furnace or boiler. The FTC set the minimum rating for new units sold to be 78 percent. For all non-weatherized gas furnaces sold in the northern United States, including Michigan, the AFUE must be 90 percent.

Lennox The website Energy.gov notes that older furnaces can have an AFUE ranging from only 56 to 70 percent if your furnace is 10 to 15 years old, it may in that range and waste energy compared to current standards. Modern, high-efficiency furnaces, however, can have an AFUE as high as 98.5 percent.

While the AFUE number is important when comparing furnaces, it’s not the only factor to consider when heating your home. The number doesn’t take into account the amount of heat loss that can occur from ducts that run through partially conditioned or unconditioned spaces such as attics. Other energy losses can occur through leaks around window and door frames that bring down the efficiency of your entire heating system.

That’s why it’s important if you’re considering a new furnace to have a comprehensive energy audit done on your home first. Bel-Aire offers energy audits as part of its service to keep you warm in winter, cool in summer, and your energy bills down year-round.