January 29, 2020

Shopping for a new furnace? If so, you probably have a lot of questions. For instance, how do you compare one furnace to another? Which one is the most energy-efficient? Are more costly units really worth the difference? Fortunately, there are some key furnaces characteristics you can use to help you choose the best system for your home. One of these is the AFUE rating.

What is the AFUE rating?

AFUE stands for annual fuel utilization efficiency. It is a standardized measure of the furnace’s energy efficiency over a one-year time period. In many ways, it is similar to the SEER rating for air-conditioners. The AFUE rating is a measure of the furnace’s heat output as a percentage of its fuel input. That can sound confusing at first, but it will be easier to understand once we break it down below.

For instance, let’s say you buy a furnace that converts 95 percent of the natural gas that it consumes into heat. That furnace has an AFUE rating of 95 percent. The other 5 percent is wasted, primarily in the form of exhaust gases. Furnace efficiencies range from about 50 percent for older, outdated furnaces to as high as 98.5 percent for new units.

What are the limitations of the AFUE rating?

Although the AFUE rating is an excellent tool that you can use to compare the energy efficiency of one furnace to another, it has limitations. For starters, the rating only applies to the furnace itself. It does not include losses in the ductwork, which can be considerable. It also does not evaluate the energy efficiency of doors, windows and other components of the building envelope.

Additionally, the AFUE rating can only be used to compare the efficiencies of furnaces using the same type of fuel. In other words, comparing the AFUE of a natural gas furnace to the AFUE of a heating oil furnace is like comparing the sweetness of apples to oranges.

How do I use AFUE ratings when shopping for a furnace?

All new furnaces and boilers must display their AFUE rating in order to comply with Federal Trade Commission (FTC) regulations. You can use these ratings to compare the efficiency of one furnace to another. Basically, the higher the AFUE, the less fuel it will consume.

However, the total lifecycle cost of a furnace will depend on its original cost, its maintenance costs and the type of fuel used. In order to properly take all of these variables into account, you may need the help of a full-service HVAC Contractor.

For a comprehensive range of HVAC services, contact Woodward Heating Air Plumbing online or by phone at (503) 749-7760.

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