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Understanding Furnace Energy Efficiency (AFUE)

wilmington nc heating and air conditioning

There is no question that furnaces have become more and more energy-efficient throughout the years. When you are looking to purchase a furnace knowing the efficiency ratings of the furnace should be included in your decision. This rating is called the AFUE.  AFUE stands for annual fuel use efficiency. This number is found by creating a ratio of useful energy out and energy input. It is the measure of the annual output of the heat through the furnace compared to the amount of annual fossil fuel energy taken in by the furnace. Basically, the higher the AFUE the higher the use efficiency.


How AFUE Affects Me


According to the EPA (Environmental Protection Agency) industry standards, the minimum rating for an unused gas furnace is 78%. For a furnace to be considered “mid-efficiency” the unit has to have an AFUE ration of 80 to 83 percent. The high-efficiency unit has a range for the average rating of 90 to 97 percent. When the furnace receives a high rating that means that more heat is being given off from the furnace than the furnace is actually consuming.


The AFUE measures the efficiency of how well the furnace compares fuel to energy. This number is tracked throughout a complete heating season. If you have a furnace that is on the high end of the AFUE, this most likely means you are receiving greater energy efficiency.


Gas Furnace


Gas furnaces are extremely efficient. Although around ten percent of the energy can escape, there is still a 90% percent energy rating. Energy has the ability to escape through the chimney or other ventilated areas. Heat loss can average around 35 percent is dependent on the duct work and the location of the ducts. Places like the garage, attic, or crawl spaces can impact the furnace energy output.


Electric Furnace


There is no chimney when it comes to electric furnaces which make the AFUE on an electric furnace anywhere from 95% to 100%. The lower end of the scale is when the furnace is installed outdoors, but the upper end would be in an average size home. An electric furnace is high in efficiency, but it also inflicts higher electricity cost. This has made the electric furnace a much less economical choice than the gas furnace.


Sometimes calculations can get too tedious to understand. The overall gist is there is a way to determine how efficient your furnace is, and if you don’t know what the AFUE for your furnace is, contact us today for consultation by one of our HVAC professionals.

Our Partners


Back in 1974, before company mission statements were in vogue, Jack Brinson started his heating and air company with one objective – treat every customer with the personal and professional care they deserve. From new installation to system replacement to service and repair, our team of heating and air professionals will do it like it’s their own home. Our rapid response time is designed with your comfort in mind. That’s the quality of service you can expect. After all, Jack wouldn’t have it any other way.