Understanding Furnace Efficiency Ratings

Posted by admin on June 15, 2015

Do you know if your furnace is efficient? For many homeowners whose furnace came with their home when purchased, it is an important variable to consider when you are looking for ways to improve your energy use. You need to know what the furnace efficiency ratings (AFUE) tell you about how your furnace works and how to determine your furnace rating if it isn’t already posted on your furnace.

What do the numbers mean?

Your furnace efficiency ratings simply tell you how much it will cost to for you to heat your home; ratings fall between 50 and 100. If the rating on your furnace is in the higher range, you can expect that you will get more heat for the amount of energy used. In other words, this means that the lower the rating is, the less efficient your furnace is, and the more that it will cost to heat your home.

What the efficiency ratings measure is how much heat the furnace will produce compared to the actual amount of energy that is needed to produce that heat. For example, if your Annual Fuel Utilization Efficiency (AFUE) rating is 90 percent, this means that 10 percent of the energy is lost, while 90 percent will become heat. However, this rating does not measure how much heat will lost through the walls or duct work in your home. In some parts of the home, up to 35 percent of heat can be lost.

How can you know that your furnace is efficient?

The federal government requires that each furnace have a sticker with the AFUE rating on it, however depending on the age of your model it may not. This rating appears on a yellow sticker that will have the percentage of heat utilized by your furnace, so you know how efficient your furnace is.

If you have an older furnace, then you might have to do some investigatory work to find out just how efficient your furnace is. Here are some things to look for:

  • Continuous pilot light. If your pilot light is always on, this is an older furnace that is not efficient. They tend to be in the 56 to 70 percent range of furnace efficient ratings. The duct work on these machines is complicated, and usually entangled.
  • Models that were built more recently and have a fan that controls the airflow also do not have a pilot light. These furnaces are likely in the 80 and 83 percent efficiency ratings range. 
  • Models that have two heat exchangers with sealed combustion units usually have furnace efficiency ratings of 90 to 98.5 percent.

Your furnace efficiency rating is important, not only because it tells you how well your furnace operates but also how much money it should cost to heat your home. If you need an estimate to learn more about replacement furnaces to bring up your rating, please contact Climate Experts.

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