Understanding AFUE Ratings

March 27, 2024

If you’re shopping for a new furnace, you’ve probably heard of AFUE ratings, but do you really know what they mean? Here’s a quick guide to what AFUE ratings mean and what to look for when choosing your furnace.


What is an AFUE Rating?

AFUE, or annual fuel utilization efficiency, is a metric that assesses the efficiency of furnaces in converting the energy from fuel into heat. Think of it like gas mileage on a car: just as good gas mileage on a car means it uses fuel efficiently, a furnace with a good AFUE rating runs efficiently. The higher the number on the AFUE rating, the higher the efficiency.

The calculation of AFUE involves dividing the fuel supplied to a furnace or boiler by the heat produced, typically measured in British Thermal Units (BTUs). The standard annual fuel input is set at one hundred million BTUs. The rating tells you what percentage of energy used by the furnace is being used to generate heat, and how much is wasted. For example, an AFUE rating of 80% means 80% of the energy used by this furnace is becoming heat while 20% of it is being wasted.

 It’s important to note that AFUE is an average rating, as fuel efficiency can vary on a day-to-day basis.


What AFUE Rating Should I Look for?

The AFUE rating you choose will depend on a few factors, such as up-front budget and how important energy efficiency is to you in your home. The minimum AFUE rating for a furnace is 80, indicating that 80% of the heat generated is transferred into the home. Mid-efficiency furnaces usually fall in the 90 to 93% AFUE range, while high-efficiency models can go from 94 to 98.5%. 


The Benefits of a High AFUE Rating

The biggest advantage of opting for a furnace with a high AFUE rating is the savings on your monthly heating bill. Lower AFUE-rated furnaces tend to dissipate more heat during operation, whereas those with higher ratings are more efficient in retaining heat, resulting in lower operating costs. The difference between a mid-range AFUE rating and a high rating can translate to substantial savings over time. A high AFUE rating also means your furnace is more environmentally friendly, so eco-conscious homeowners often prefer to opt for a high AFUE rating. In Canada and British Columbia, only appliances with a higher AFUE rating are allowed to be sold due to changing regulations. The minimum we typically see is 95% efficiency. 

If you are interested in upgrading to a more efficient furnace, get in touch with the pros at John Sadler Plumbing & Heating today! We are happy to answer any questions you may have and provide recommendations for the right solutions for your home.

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