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Understanding the Difference Between Mid Range and High AFUE Furnaces

Learn more about AFUE ratings and furnace technology.

AFUE Furnaces

Are you shopping for a new furnace? You’re going to be hearing a lot about AFUE or Annual Fuel Utilization Efficiency. While it may seem obvious that a higher AFUE is better, it will still be helpful to understand more about AFUE and how furnaces with mid-range and high AFUEs differ.

What AFUE Really Means

AFUE is measured as a percentage that tells you how much fuel gets turned into heat by the furnace. So if you choose a high-efficiency furnace with an AFUE of 95 percent, this means the furnace is turning 95 percent of the fuel it consumes for into heat for your HVAC system. Heat lost through the flue or in the process of the furnace cycling on and off accounts for the other 5 percent of the fuel you’re paying for.

It is extremely important to remember that the AFUE is based on ideal laboratory conditions. It does not represent the actual percentage of fuel that gets turned into useable heat that you feel coming out of your air vents.

The amount of heat that makes it to the rooms in your home will be affected by the state of your ductwork, including the existence of any gaps or holes in the ducts and the quality of the insulation around the ducts, as well as the overall amount of air loss occurring in your home. In some cases, these kinds of factors can cause additional heat loss at up to 30 percent, which will reduce the actual efficiency you’re getting from your heating system.

Mid Efficiency Furnaces: 80 percent AFUE

Thanks to DOE mandates, 80 percent AFUE is actually the lowest rating you can find for a new furnace. This still represents an improvement over the furnaces of decades past which hovered around 75 percent.

80 percent AFUE furnaces are available in a variety of different styles, but the best one to choose is a two-stage furnace. This type of furnace has a high/low capability allowing it to modulate output to suit both the coldest days and warmer ones. This capability helps the system operate at peak efficiency and can save you money on your heating bills.

What AFUE Really Means

Furnaces start to be considered high efficiency at 90 percent AFUE, though models area available with up to 98 percent AFUE. The higher rate of efficiency is achieved by incorporating condensing technology. Whereas an ordinary furnace loses a lot of heat to hot flue gases, a condensing furnace prevents this heat loss by cooling and condensing the exhaust before it is vented outside and sending the captured heat into your ductwork.

Condensing furnaces also come with two-stage capability and are almost always paired with a variable speed fan as well.

Need Help Choosing a New Furnace?

If you are shopping for a new furnace, AFUE is important but it is not the only factor to be considered. Fortunately, you can get help choosing the right furnace for your specific needs and budget by contacting Econo West Heating Air & Plumbing. We will also provide professional installation to make sure your new furnace performs as expected.

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