What is the AFUE Rating for Furnaces?

If you’re looking for a new furnace, one of the first things you’ll need to consider is the AFUE rating of the unit.

AFUE stands for Annual Fuel Utilization Efficiency, which is expressed as a percentage. The percentage is a reflection of how much heat is produced by the furnace for every dollar of fuel it consumes.

Let’s look at an example: With an 80% AFUE unit, 80% of the heat produced by the furnace goes directly towards heating your home. The remaining 20% of heat is vented outside with exhaust gases, so it’s considered “wasted” heat. Said another way, with an 80% furnace, you waste $0.20 of every dollar you spend on fuel to heat your home.

Furnaces with higher AFUE percentages waste less fuel to heat your home, which makes them more energy efficient. However, because these energy-efficient furnaces rely on more advanced technology, the equipment is more expensive.

We know you probably have more questions, such as:

  • What is a “good” AFUE percentage?

  • Which AFUE percentage should I choose for my new furnace?

We’ll answer both of these questions below.


Want a professional to help you choose an AFUE rating for your new furnace? Call us at 503-538-1950 or schedule an appointment online to meet with one of our comfort advisors.

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What is a “good” AFUE percentage?

Most new furnaces fall into one of the following categories:

  1. Mid-efficiency, standard units, which range from 80% to 89% AFUE

  2. High-efficiency, condensing units, which range from 90% to 98% AFUE

When we talk about “good” AFUE percentages, the term is somewhat relative. Compared to older furnaces that had AFUE percentages ranging from 50% to 70%, any new furnace with an AFUE percentage of 80% or higher is a big improvement and will cut down energy costs considerably.

That said, the best furnace you can buy is a high-efficiency, condensing furnace. Condensing furnaces are able to extract more heat from the same amount of fuel as a mid-efficiency unit, which ultimately gives you higher energy savings in the long run.

However, this extra energy efficiency comes with a higher price tag: Condensing units have additional parts (a second heat exchanger) and require special condensate drainage, which makes them more expensive to install.

So the question is this: Is a high-efficiency furnace worth the higher investment?

It depends on the factors below...

Which AFUE percentage should I choose for my new furnace?

If you’re debating whether to invest in a standard, mid-efficiency furnace or a high-efficiency unit, you’ll want to consider the following factors.

  • Your budget: High-efficiency furnaces can be $500 to $1,000 more expensive than a mid-efficiency unit. If you’re on a tight budget, you might consider sticking with a mid-efficiency furnace.

  • Your home’s insulation levels: If your home is poorly-insulated, then your furnace will have to work harder to keep your house warm, which increases your energy bills. Installing a high-efficiency furnace in a poorly-insulated home doesn’t make sense because the furnace would have to work overtime heating your home, which cancels out the energy savings provided by the high-efficiency system.

  • The condition of your ductwork: Similar to your home’s insulation levels, the condition of your ductwork will also determine your overall energy savings. Leaky or disconnected ducts make your furnace work harder to keep your home warm, which could ultimately cancel out the energy savings provided by a high-efficiency system.

Because you may not know the condition of your home’s ductwork or how well-insulated your home is, we recommend consulting with a professional to help you make the decision. A professional can help weigh these factors and calculate the projected savings of a particular furnace, which can help you know which AFUE rating you should get for your new system.

Ready to consult with a Portland furnace expert?

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One of our trusted comfort advisors can help you compare different furnaces and weigh the factors we listed above so that you choose the best furnace for your home.

When you work with Four Seasons, you can count on fair, honest pricing and transparent recommendations from our team of heating experts. Learn more about what to expect when you work with us by visiting our furnace installation page.


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