AFUE is an acronym that expresses the energy-efficiency of natural gas and oil-fired furnaces. Short for Annual Fuel Utilization Efficiency, it’s the primary metric used to help consumers compare the efficiency of new furnaces in order to determine which provide the most savings in combination with the best heating performance. When shopping for a new furnace, you’ll find its AFUE rating prominently displayed on the Department Of Energy’s yellow EnergyGuide sticker affixed to every new unit.

What AFUE Means to You

Annual Fuel Utilization Efficiency is simply a percentage that tells you how much of the fuel consumed by a furnace produces usable heat vs. the amount of heat lost in the combustion process. All gas and oil furnaces lose some heat — mainly in the form of hot gasses exhausted up the furnace vent pipe.

Standard vs. High Efficiency

The federal minimum Annual Fuel Utilization Efficiency for a standard-efficiency gas furnace is 80. That means 80% of the heat generated actually warms your house while the balance — 20% — is lost in the combustion process. High-efficiency units known as “condensing furnaces” incorporate additional technology like a secondary heat exchanger to recover lost heat and offer ratings as high as 95 percent.

Is High Efficiency Always Better?

High-efficiency furnaces come with an initial purchase price substantially higher than a standard AFUE-80 model. While these units produce more heat with less fuel consumption, savings from lower operating costs may still take some years to compensate for the higher upfront price. Whether the extended payback period makes good financial sense or not depends largely on the length of your local heating season and how long you plan to live in the home.

What About Electric Furnaces?

Since electric furnaces have no combustion losses, all are rated with an AFUE of 99%. However, this nearly perfect efficiency doesn’t mean electric heating is more economical. Because of the substantially higher cost of electricity vs. natural gas in most regions of the country, electric heating is always more expensive.

For more about using AFUE to shop for your next heating system, contact Apollo Home Heating, Cooling, Electrical and Plumbing.