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What Is the AFUE Rating?


If you are the owner of a combustion heating system, either a furnace or a boiler, or are in the market for a new combustion heating system, you are going to want to know the AFUE of your system. Just as a car is rated by its miles per gallon (mpg), combustion heating systems are rated by AFUE. This rating is very important in determining how efficient your existing heater is operating, or how efficient a new heater will operate. We’ll explain more below.

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What the Acronym Means

The acronym AFUE stands for annual fuel utilization efficiency. The rating is expressed in a percentage. There is a minimum standard rating for combustion systems, and that rating is 78%. This means any new heating system you purchase will have an AFUE of at least 78%. However, the AFUE scale goes to 100%, so it’s important to keep this in mind if you are looking for a new heater.

The important information to understand about AFUE is what it tells you, which is how efficiently a particular system uses fuel. For instance, a boiler with an AFUE of 83% uses 83% of the fuel you purchase and converts is to useful energy, i.e., heat. The other 17% is lost in combustion byproducts that are expelled through your flue. As you can see, the information AFUE provides is critical to understanding the energy efficiency your existing or new furnace provides.

What AFUE Doesn’t Tell You

It can be easy to mistake that a high AFUE rating means that a certain type of heater will provide your home with more heat than another. This is not what the AFUE rating tells you. What the rating tells you is that a certain heater will heat your home using less fuel than another.

Confused by AFUE? You don’t have to be. Just give the experts at Design Air Inc and let us help you with your heating system in Ramsey, NJ!