What Does AFUE Rating Really Mean?

image of efficiency depicting AFUE ratings of heating systems

Energy Star estimates that almost 50% of the total cost of your home’s energy can be attributed to your cooling and heating system. If you want to reduce your energy costs, this is one area where you need to make smart decisions, especially about repairs, replacements, and system maintenance. With heating systems, it is important that you understand how the AFUE rating works because it has a direct impact on your energy consumption and ultimately, your energy bills. Let’s take a closer look at the AFUE rating and what you need to know about it.

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What Is An AFUE Rating?

AFUE stands for Annual Fuel Utilization Efficiency. It is a rating that appears as a percentage. The American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHARE) developed the AFUE rating to gauge how energy-efficient a heating system is. It measures the ratio of heat produced versus the amount of fuel that the heating unit consumes. This is why this rating appears on water heaters, furnaces, and boilers.

British Thermal Units

To determine the AFUE rating of a heater, for example, you could take the amount of fuel used by the heating unit and divide it using the amount of heat it generated. This amount is expressed in BTUs or British thermal units. The higher the rating, the more efficient the unit.

For example, a heating system that has an AFUE rating of 85% means that the system utilizes 85% of the fuel it consumes to generate heat. The remaining 15% is lost due to the inefficiency of burners and chimneys. Note that AFUE does not calculate for heat that is lost in the HVAC ductwork and piping. How much heat is lost can be critical. The U.S. DOE (Dept. of Energy) states that ducts in attics and other unconditioned areas could lose about 35% of the energy output of the furnace.

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Heating Season Performance Factor

A high-efficiency heating unit typically has a high AFUE rating. What this rating ultimately means is that you get to enjoy lower fuel costs. Note that electric heat pumps are not equipped with an AFUE rating. Instead, the efficiency of these systems is measured using HSPF (Heating Season Performance Factor).

The AFUE rating is a measurement standard used nationwide promoted by the US Department of Energy. The DOE helps promote energy efficiency by setting the minimum ratings for all combustible heating systems through the AFUE rating. Currently, the minimum set is 80% for the Southwest region and 90% for the Northern region. Most new models of furnaces that are manufactured today come with an AFUE rating of at least 90%.


Identifying The AFUE Rating

image of a furnace and manufacturer sticker

All manufacturers of boiler and furnace systems are required by the Federal Trade Commission to provide information about the AFUE ratings of the products they sell. In most units, the AFUE rating can be found on the EnergyGuide label. This is the yellow-colored tag that can be found on the appliance. If the AFUE rating is not indicated on the unit, you can check the websites of the manufacturer and the retailer. In some cases, it is indicated in the owner’s manual.

It is also worth noting that all heating systems lose their efficiency as they age. This means that the AFUE rating provided by the manufacturer will be higher compared the actual rating of the system. If you want to know how efficient your system is, get in touch with a professional HVAC technician.

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What AFUE Rating Should I Look For?

image of efficiency rating of a home heating system

The DOE suggests looking for a heating system that has an AFUE rating that is over 80% if you live in the Southwest and over 90% if you live in the Northwest. Note that heating systems will lose their efficiency over the years.

Old heating systems and underperforming heating systems can even have AFUE ratings of 70% or even 56%. The standards set by the DOE are at 78%. Based on these standards, heating systems are classified based on their AFUE rating. A system with a lower than 80% rating, for example, is classified as low-efficiency. A system that has a rating of 80% to 89% is considered mid-efficiency, while a system with an AFUE rating of at least 90% is considered high-efficiency.

Even with very high-efficiency ratings, there are still inefficiencies that heating systems can suffer from, such as distribution and firing losses. This is why it is not likely that you will find a system with an AFUE rating of 100%. At most, you will get one that has a 97% to 98.5%.

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Why An AFUE Rating Is Important For The Homeowner

Because AFUE ratings measure the efficiency of a furnace, homeowners can use these figures to determine the best-performing system to buy. Furnaces will, of course, lose their efficiency over time, which means that older furnaces will have a low AFUE value. Prior to 1975, heating systems in the United States were not required to meet the minimum AFUE ratings. In 1987, the DOE set the AFUE rating at a minimum of 78%. In 2015, this figure was raised to 80%. Any furnace that is at least 15 years old is likely inefficient and more costly to run.

By replacing the unit with a new unit, even one that has a low-efficiency rating of 80%, you will still enjoy greater energy savings. If you want to save more, choose a heating system that has a higher AFUE rating. Right now, the best systems have an AFUE rating of 98.5%. Whatever AFUE rating the appliance has that you decide to buy will significantly affect your carbon footprint and energy bills.


Why Should I Choose A High-Efficiency Furnace?

There are several factors that come into play. First, consider your location. The colder the region where you are, the more you will use the furnace. This is why you should consider a furnace with high efficiency. With a high-efficiency furnace, you can enjoy as much as 18.5% more energy efficiency compared to a lower-efficiency system. On average, households in the U.S. pay at least $600 annually for heating alone. With a high-efficiency system, it is likely you can save around $111 each year.

Next, take a look at your budget. High-efficiency furnaces carry a price tag of around $1,000 at the very least, compared to mid-efficient furnaces. Heating systems typically have a lifespan of 15-20 years. So if you can save $111 for at least 15 years, you could save a total of around $1,600. That means that you will be able to recoup the cost of installation for the system.

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What To Expect From High-AFUE Furnaces

In general, high-AFUE systems use the latest technologies and are designed with features that deliver excellent energy efficiency. They are designed with standout features such as:

  • Variable speed blowers
  • Variable heat output
  • Secondary heat exchanger
  • Improved air filtration
  • Direct spark ignition



The AFUE rating is an important number to consider when investing in a new heating system. The US Dept. of Energy sets the standards that all heating systems must meet to be considered energy-efficient. In the U.S., all furnaces carry a minimum of 80% AFUE rating.

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Call Hart Home Comfort For Your Home Heating Requirements

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Our company has the most competitive and affordable HVAC service costs in the area. When you need to replace your HVAC system, we can recommend the best and most budget-friendly unit for your home. We back all of the work we perform with a guarantee. Schedule an appointment with Hart Home Comfort today for a free, in-home estimate.

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