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What is a Furnace’s AFUE Rating?

Published: January 8, 2014
Technician inspecting furnace

small_363042911When you’re looking for a new furnace, one of the most important factors you need to consider is the AFUE rating of the system you choose. Today we’re going to talk about what an AFUE rating is and how you should use it when buying a new heating system for your Metro East home!

What is an AFUE rating?

AFUE stands for “annual fuel utilization efficiency.” It is a number (given as a percentage) that describes the energy-efficiency of a furnace over the course of a typical heating season. In particular, it describes the percentage of natural gas a furnace consumes that it is able to turn into useful heat for your home.

As an example, a furnace with a 90% AFUE rating is able to turn 90 percent of the fuel it consumes into useful heat. The other 10 percent is lost as exhaust.

What is the minimum allowed AFUE rating?

There are no restrictions on how low of an AFUE rating you can have for an existing furnace. In fact, some older furnaces might have AFUE ratings as low as 55 percent.  However, the current federal minimum for the AFUE rating of a newly-installed furnace is 78 percent. In addition, there is currently legislation on hold that will attempt to raise this minimum to 90 percent.

What is a good AFUE rating for a new furnace?

When you’re comparing new furnaces, it’s important to keep in mind that a higher AFUE rating will translate to lower operating costs over the lifetime of a given system. If you have an old, inefficient furnace in your home, you can see some substantial savings just by upgrading to a furnace that meets the current minimum AFUE rating of 78 percent.

For maximum efficiency, you should consider installing a furnace with an AFUE rating of at least 90 percent. A furnace that meets this standard is considered a high efficiency system because it utilizes a second heat exchanger to extract heat from the exhaust gas that would normally be carried out of your home. Although high efficiency furnaces cost more up-front, you can recoup much (if not all) of the extra investment due to lower operating costs over the system’s lifetime.

If you have any questions about the AFUE rating of a furnace, or if you’d like a heating system serviced or installed in your home, contact Tiger, your St. Louis Metro East plumbing, heating and air conditioning contractor.

photo credit: Unhindered by Talent via photopin cc

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