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June 30, 2021

AFUE Rating – What is it and What Is Considered “Good”?

AFUE is one of the most important measures for heating appliances, including furnaces, boilers, or water heaters. If you haven’t heard the term AFUE before or don’t know exactly what it means – don’t worry, you aren’t alone.

An AFUE (Annual Fuel Utilization Efficiency) rating – often displayed on a yellow sticker on the unit – is an efficiency measure that represents the amount of fuel that is consumed by your equipment compared to the amount of energy produced by the equipment over the course of a year.

What does the AFUE rating tell you about your equipment?

Here’s an example: in a 90 AFUE furnace unit, 90 percent of the fuel consumed by the machine results in heat for your home; the other 10 percent is lost somewhere in the delivery chain (usually up the flue).

Another way to look at how AFUE works is by using money as an analogy. For every dollar you spend on heating oil or propane for an 80 AFUE boiler, 80 cents go toward heating your home’s air; In a 95 AFUE furnace, that number jumps up to 95 cents. As you see, that can make a big difference in your energy bill over time.

What’s a typical AFUE rating for a furnace?

A lot depends on how old your furnace is and the fuel it uses. Older, less efficient furnaces have considerably lower AFUE ratings than newer models – especially if they have not been properly maintained by a heating professional. Most gas furnaces and boilers have AFUE ratings between 80% and 98%. It’s a little narrower for oil furnaces. Most have AFUE ratings between 81% and 87%. A few have ratings above 90% AFUE.

The U.S. Department of Energy has some standard efficiency guidelines for furnaces:

Low efficiency (older systems): 56-70 percent AFUE

Mid-efficiency (older or newer systems): 80-85 percent AFUE

High efficiency (mostly newer systems): 90-98.5 percent AFUE

As of 2015, the minimum standard AFUE for new furnaces Is 80 percent.

Should I Buy the Highest AFUE Furnace?

Not necessarily. As the AFUE increases, furnace cost goes up. Furnaces that are 90% efficient and higher have a secondary heat exchanger which means more parts/equipment and higher cost. Also, the most efficient furnaces are two-stage and variable capacity furnaces. Meaning,  they heat in stages, either two stages (low/high) or modulating stages between about 40% and 100% of capacity. Staged heating, especially variable capacity heating, requires equipment that is more expensive than single-stage furnaces.

If you live in a warmer climate, paying more for a 90% furnace, especially if it is a 2-stage or variable capacity furnace, won’t pay for itself for many years. However, paying more for a 90% furnace in a colder climate could pay for itself in just a few years because it reduces you annual heating bill.

Of course, AFUE doesn’t tell the whole heating efficiency story – the air tightness of your home, how well you maintain your equipment, the condition of your ducts, and how well your heating equipment was installed all come into play when determining how much heating bang you get for your buck. If you need help with choosing a new furnace, give us a call!

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