What Does AFUE Rating Really Mean?

image of energy efficiency and home heating hvac systemAccording to Energy Star, your home’s cooling and heating system accounts for nearly 50% of your total energy costs. Therefore, one way to cut your energy costs is to make smart decisions regarding the system’s maintenance, repairs, and replacements. For heating systems, you should be extremely familiar with AFUE because it directly affects your energy usage and energy bills. Here’s everything you need to know about AFUE rating.

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The Definition Of AFUE Rating

Created by the American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHARE) and represented as a percentage, the Annual Fuel Utilization Efficiency (AFUE) is basically a measure of the energy efficiency of a heating system, such as a water heater, boiler, or furnace. In general, you can define AFUE as the ratio of the heat produced compared with the total amount of fuel consumed by the heating unit.

Therefore, to calculate your heater’s AFUE rating, simply divide the amount of fuel consumed by the unit by the amount of heat generated, usually in British thermal unit (BTU). If your system has an AFUE value of, say, 85%, it means it uses 85% of the fuel energy for heating and loses the remainder (15%) to inefficient burners, chimneys, and elsewhere. It’s worth noting that AFUE does not account for the heat lost in HVAC piping and ductwork. The amount of heat lost could be significant. According to the US Department of Energy (DOE), ducts located in garages, attics, and other unconditioned spaces could lose as much as 35% of the furnace energy output.

A high AFUE value typically means greater energy efficiency and vice versa. To put it another way, high AFUE ratings mean lower fuel costs. It’s worth noting that, in heating mode, electric heat pumps do not use AFUE. Instead, they use Heating Season Performance Factor (HSPF). Today, AFUE is a national measurement standard used by the US Department of Energy to denote the combustion efficiency of a heating system.

To promote energy efficiency across the country, the DOE sets the minimum AFUE ratings for gas heating systems, which are currently at 80% and 90% for the Southwest and Northern regions, respectively. Consequently, almost all new furnaces being produced today have AFUE ratings of 90% or better.

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How To Find The AFUE Rating

To help consumers make informed purchase decisions, the Federal Trade Commission requires boiler and furnace manufacturers to provide AFUE ratings for their products. Most manufacturers include this information in the EnergyGuide label, which is the yellow tag found on most electrical appliances. If the rating is not on the EnergyGuide label or you can’t locate the label, check the manufacturer’s or retailer’s website or your owner’s manual. Keep in mind heating systems typically get less energy efficient over time. Therefore, the manufacturer’s printed AFUE rating will likely be higher than your system’s actual rating. For this reason, you should get a professional HVAC technician to measure your system’s actual AFUE rating.

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What Is A Good AFUE Rating?

homeowner saving money due to low home heating bills

According to the DOE, a good AFUE rating is anything above 80% for the Southwest and 90% for the Northwest region. However, over time, heating systems typically get less efficient. In fact, the AFUE ratings for under-performing or old heating systems can be as low as 56% to 70%. The DOE standards mandate that new systems have AFUE values of at least 78%. Based on AFUE ratings, heating systems are classified as either low-efficiency systems (less than 80%), mid-efficiency systems (80% to 89%), and high-efficiency systems (90% or higher). Because of the inefficiencies associated with heating systems, including firing and distribution losses, the highest AFUE rating is around 97% to 98.5%.

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How Can Homeowners Use AFUE Ratings?

AFUE rating is a measure of how efficiently a furnace operates. Furnaces generally lose efficiency over time, meaning older and non-efficient furnaces tend to have lower AFUE ratings. Before 1975, the heating systems sold in the US did not have to meet any minimum AFUE ratings. The DOE set the minimum AFUE rating at 78% in 1987 and then raised it to 80% in 2015. Furnaces aged 15 years or older are usually energy inefficient, and therefore, expensive to run. Replacing it with even a low-efficiency 80% AFUE will lead to greater energy savings and lower energy bills. For even more savings, choose a furnace with a higher rating. The most energy-efficient systems on the market today top out at around 98.5% AFUE. The AFUE rating you choose will have a significant impact on your energy bills and carbon footprint.

Should I Buy A High-Efficiency Furnace?

To answer this question, you need to consider several factors. Firstly, you need to consider where you live. If you live in a particularly cold region, and therefore, use a furnace often, a high-efficiency furnace is the best option because it will deliver greater energy savings over time. A high-efficiency furnace can be up to 18.5% more energy efficient than a low-efficiency system. Figures from various studies show that on average, American households spend around $600 or more on heating per year. This means that with a high-efficiency system, you could save as much as $111 every year.

Secondly, you need to consider your budget. On average, high-efficiency furnaces cost about $1,000 more than mid-efficiency furnaces. However, furnaces, in general, have a life expectancy of 15 to 20 years. Therefore, if you save $111 for 15 years, that’ll add up to more than $1,600. Therefore, over time, you’ll be able to recoup the additional cost of installing the system.


Features of High AFUE Furnaces

High AFUE furnaces generally leverage new technologies and features to deliver unmatched energy efficiency. Some of the standout features found on such systems include:

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


AFUE is a measure of the energy efficiency of a heating system. The US Department of Energy uses it to set standards for furnace efficiency. All furnaces sold in the US must have an AFUE of 80% or higher.

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McAllister Energy

McAllister Energy offers high-quality HVAC services in Camden County, New Jersey. We hire only the best professionally certified technicians who conduct superior heating and cooling services. Some of our HVAC services include HVAC maintenance, heating and cooling installations, repairs, ductless systems, energy audits, and much more. All our techs provide accurate HVAC services on time, every time.

Our company guarantees affordable heating and cooling service rates. Our maintenance services can increase your home’s comfort, energy efficiency, and cost-effectiveness. We can also provide you with a highly energy-efficient HVAC replacement system that fits your budget. Your satisfaction is important to us, so all our work comes with a guarantee. Book a service appointment with McAllister Energy today. We provide free, in-home estimates.

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