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AFUE Ratings Explained

Every type of HVAC equipment has its own efficiency rating system, and for boilers and furnaces, that system is called the annual fuel utilization efficiency, or the AFUE. The higher the AFUE rating, the more efficient the boiler or furnace is. Understanding these ratings is important so you can demonstrate to your customers the efficiency of their current furnace or boiler, and explain why an upgrade or replacement may provide long-term cost savings by increasing efficiency.

What is AFUE?

The AFUE is a measurement that demonstrates how efficient a boiler or furnace is at converting its fuel into heat. It is required to be displayed on all new furnaces and boilers, so finding the AFUE is as simple as reading the label. But what exactly does the figure you see mean? Essentially, the AFUE represents the ratio of heat output versus the fossil fuel energy that was consumed.

For example, if a furnace or boiler has an AFUE rating of 80%, that means 80% of the energy from the fuel source was converted into heat for the home, and the remaining 20% escaped through the chimney or somewhere else. NOTE: The AFUE rating does not account for the heat that escapes through the ductwork or piping once it leaves the furnace or boiler, which can be as high as 35% depending on where it is located.

What About Electric Furnaces or Boilers?

When looking at AFUE ratings, you will notice that electric appliances usually earn the highest marks. They are the most efficient at turning the entire energy source into heat. However, there is a caveat: the cost of electricity is often much higher than the cost of gas or oil, so while the AFUE rating may be higher, it might still cost more to operate over the course of a year.

Identifying AFUE by Equipment Features

While comparing AFUE ratings is a great way to determine efficiency, you can also judge how efficient a furnace or boiler is depending on the features it contains:

  • Low-efficiency systems (AFUE of 56% – 70%) will often have a continuous pilot light, a heavy heat exchanger, and little-to-no control over the flow of combustion gases.
  • Mid-efficiency systems (AFUE of 80% – 83%) will usually have an electronic ignition instead of a pilot light. They feature an exhaust fan that controls the flow of combustion gases more effectively and a flue pipe with a small diameter. They are usually smaller and lighter in weight.
  • High-efficiency systems (AFUE of 90% – 98.5%) usually feature a sealed combustion and have a second heat exchanger that condenses the flue gases.

We Can Help with Furnace and Boiler Efficiency

If your customers are looking to increase efficiency in their home, there are many solutions you can offer, including upgrading the ductwork, adding in zone control, and installing a programmable thermostat or smart thermostat. Sometimes, replacement is the simplest, most cost-effective solution, and we can help with that, too.

If your customer wants a more efficient furnace or boiler so they can reduce their heating expenses, contact us today. We would love to help you choose the best system for their needs.