Understanding Furnace Efficiency

Shopping for a new furnace can be extremely time consuming and sometimes a bit overwhelming. Without knowing exactly what to look for, you may not know if a furnace is compatible with your current HVAC system or if your new furnace is more or less energy efficient than your last. Keep reading to learn how furnace efficiency is measured and how it affects your home’s heating and cooling system.

Furnace Efficiency: How Is It Measured?

A furnace’s efficiency rating is measured by the annual fuel utilization efficiency (AFUE). The United States’ Federal Trade Commission requires all furnace efficiency ratings to be displayed for consumers in order to provide the consumer with the most information possible when purchasing a furnace.

AFUE is the measurement of how much fuel is directly converted to heat by a furnace. For example, a gas furnace with an 80 percent AFUE is 80 percent energy efficient—or 80 percent of gas is directly converted to heat, while 20 percent of gas is lost elsewhere in your HVAC system.

Minimum AFUE Ratings for Furnaces

According to the U.S. Department of Energy, the minimum AFUE ratings for non-weatherized furnaces and weatherized furnaces (beginning January 1, 2015) are:

Product Class

Minimum AFUE Rating

Non-weatherized gas furnaces (not including mobile home furnaces)


Mobile home gas furnaces


Non-weatherized oil-fired furnaces (not including mobile home furnaces)


Mobile home oil-fired furnaces


Weatherized gas furnaces


Weatherized oil-fired furnaces


Electric furnaces


Currently, the minimum AFUE rating for all non-mobile home furnaces is at least 78 percent, while a mobile-home’s minimum AFUE rating is 75 percent. To learn more about furnace efficiency and what furnace is best for your home, contact your local HVAC contractor.

Furnace Installation, Maintenance & Repair from T.E. Spall & Son

T.E. Spall & Son installs, repairs, and performs furnace maintenance in the Scranton and Wilkes-Barre, Pennsylvania areas. We have provided top-quality HVAC products and services since 1985 and have installed hundreds of new furnaces in northeastern Pennsylvania. To schedule your HVAC service, give us a call at (877) 591-7508(877) 591-7508 or contact us online!

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