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Nov 2, 2020 11:55:00 AM by Joe Berardi

AFUE Rating? What the $#%@ is That?!

What is AFUE rating

If you are an HVAC novice, you may wonder what AFUE is...In this article, we are here to let you know!

What is AFUE?

AFUE, or Annual Fuel Utilization Efficiency, is a rating system for furnaces and boilers that determines how much energy goes toward providing your home with heat and how much is wasted. 
For example, if you own a furnace with an 80% AFUE rating, 80% of the heat energy is in your home and 20% of it is wasted. If you own a furnace with a 90% AFUE rating, 90% of the heat energy goes toward heating your home and only 10% is wasted.
You may be wondering, "how does this really affect me, though?" Well, you pay for 100% of the energy, regardless of what is wasted! So why would a person choose to buy an 80% furnace instead of a 90% furnace? It all comes down to cost. A 90% furnace will cost you more money upfront due to its higher efficiency. But utilizing the extra 10% that is no longer lost will provide energy savings that can cover the original cost over time.

80% Vs. 90% Furnace: What's the Difference?

80% vs 90% furnace
In order to look at the differences between the two, let's begin with the basics. The 20% loss of heat energy from an 80% furnace is discarded through its exhaust system, through a vent to the outside.  A 90% furnace contains a secondary heat exchanger. This secondary heat exchanger is a component that retains lost gasses by diverting them into a condensing phase. Through this diversion, the 90% furnace retains more heat, which in turn will lower your energy bills.

80% furnace

A basic, single-stage 80% furnace has a single-speed blower motor that's only functions are on and off. It runs at full output or no output, without any variance in speed. Once it fires fully, it stays on full blast until the home is warm; once warmed, the blower shuts off. When the house is no longer warm, the process repeats. Constantly cycling on and off combined with moving air at a single speed has proved to be an inefficient way to heat a home. 
There are other options when it comes to 80% furnaces that improve efficiency, like two-stage furnaces. A two-stage furnace operates on a high or low heat output setting depending on how much heat your home needs to reduce temperature swings and lower energy bills.

90% furnace

A 90% furnace not only burns gas more efficiently but also has plenty of available options to increase energy savings and improve comfort levels in your home. Many 90% furnaces come with an ECM (electronically communicating) blower motor which allows for continuous operation at variable speeds. This process creates a more consistent temperature throughout the home.
Moreover, a 90% furnace paired with a two-stage burner can fire at a lower output and only fire at full capacity when needed, therefore improving efficiency compared to a single-stage. Running continuously at a lower speed rather than cycling on and off generates greater efficiency and effectiveness.

standard vs high efficiency furnace

What Other Types of Furnaces are There?

Easy! As explained above, we have both the 80% and 90% AFUE furnaces. We have discussed both single-stage (all on, all off) and two-stage (low and high operation). A two-stage variable speed furnace utilizes the same low and high operation as a regular two-stage furnace, but adds a higher efficiency motor that is quieter and evens out temperature difference in the home even better.
Lastly, the 'top-of-the-line' style furnace, is a modulating variable speed furnace. They provide extraordinary efficiency and comfort. A modulating system contains a burner that adjusts the amount of fuel burned incrementally to control temperature at a more consistent rate. Through this process, combined with a variable or multi-speed blower, a modulating furnace can maintain the home's temperature within a degree or two of the temperature set by a thermostat. 

What is Best for My Home?

Though there is no easy answer, ECI can provide you with a free in-home consultation, in which we can examine your existing system and make recommendations of what we think suits your home and family's needs. By doing this, we are able to inform you, the homeowner, with factual information regarding different systems, designs, and capabilities that will solve all of your heating concerns. 

ECI Comfort specializes in installing gas furnaces. Learn more about these opportunities by clicking the button below, or give us a call at 215-245-3200.
Request a Free Heating Consultation!

This entry was posted in Heating, Efficiency, AFUE

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