gas furnace flame

What Is AFUE?

When you decide to replace your heating equipment, you need the best value for your budget. Understanding how an AFUE rating works can help you choose a furnace that will use energy efficiently and lower your utility bills.

What is the AFUE Rating?

A furnace’s AFUE (Annual Fuel Utilization Efficiency) rating is a percentage used for showing how efficient the furnace is when it uses fuel. The higher the rating, the more heat you get out of each unit of fuel that the furnace uses, and the more efficient the furnace is.

The Federal Trade Commission requires all furnaces and boilers to show their AFUE rating so that buyers can easily tell how efficient they are. However, this does you little good if you’re not sure what the number means or how to interpret it. To avoid confusion, let’s use a furnace with an AFUE of 90 percent as an example.

  • If a furnace’s AFUE rating is 90 percent, this means that 90 percent of the energy from the fuel used by the furnace will heat a home.

  • Only 10 percent of the energy will get wasted by the equipment through heat loss.

Buyers should remember that the AFUE does not account for heat losses from other components of their home’s HVAC system. Unsealed air ducts can be responsible for up to 35 percent of your HVAC system’s heat loss. Even if you own an electric furnace with a 100 percent AFUE rating, leaky ductwork could downplay your heating equipment’s efficiency and drive up your electric bill.

How to Interpret Your Furnace’s AFUE Rating

To maintain your furnace’s AFUE rating and prevent breakdowns, changing the air filters periodically (before they become clogged with dust) is essential. To improve your current furnace’s efficiency, regular maintenance and retrofitting are the best options.

When you go shopping for a new furnace, look at the AFUE rating. Remember: a higher rating means greater energy efficiency, which means lower energy bills. Here is how the EPA categorizes different levels of AFUE:

  • High-Efficiency AFUE: 90 to 98.5 percent

  • Mid-Efficiency AFUE: 80-83 percent

  • Minimum Standard AFUE: 78 percent

  • All-Electric Furnaces: 95-100 percent

Higher AFUE Ratings Equate to More Energy Savings

Average energy savings associated with AFUE percentages

After you buy the right furnace for your home, make sure it is professionally installed so that it can achieve its best possible performance. Beyond that, invest in one maintenance appointment a year to keep the equipment running at peak performance.


Looking for a more energy-efficient heating system? Count on Monarch Home Services for guidance. Call (661) 271-6099 or contact us online for service!


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