Gas Furnace AFUE Definition | HVAC TerminologyGas Furnace AFUE Definition | HVAC Terminology. AFUE or Annual Fuel Utilization Efficiency Heating systems consume approximately 35% to 50% of a typical home’s energy budget. Therefore the government has come up with a way to measure efficiency ratings of furnaces so the can set a standard for minimum efficiencies. The definition of AFUE is: Annual Fuel Utilization Efficiency. AFUE is a rating that reflects how efficient a gas furnace converts fuel to energy. A gas furnace with an AFUE of 95 means that approximately 95 percent of the fuel is utilized to provide warmth to your home, while the remaining 10 percent flows up the flue and into the atmosphere. Therefore you are actually using 95% of the fuel you are paying for and the other 5% is being wasted up the flue vent.

Gas Furnace AFUE Definition | HVAC Terminology

A gas furnace with an AFUE (Annual Fuel Utilization Efficiency) of 95% is on of the highest efficiency gas furnaces you buy on the market today. Modern gas furnace engineers cannot build a furnace that gets any high efficiency simply because of the properties of natural gas and propane (LP) gas used for the fuel in high efficient high AFUE gas furnaces. The next time you go shopping for a gas furnace, make sure you take a look at AFUE ratings because this will affect the amount you pay for the fuel whether it is natural gas or whether it is propane gas. The higher the AFUE rating the lower your bill for fuel will be thereby saving you money in the long term if you choose a higher efficient gas furnace over a lower efficient gas furnace. AFUE relates to both oil and gas furnaces and boilers.

Gas Furnace AFUE Definition | Fuel Costs and Efficiency

The rising prices of fuels gives people incentives to pay higher initial installation cost for the high AFUE equipment. A higher AFUE furnace will pay for itself faster over the long term. Simply because it uses less fuel to produce the same amount of heat a lower AFUE rated furnace produces. Other considerations for purchasing the higher AFUE rated appliances is that some utilities and government agencies will give you a rebate. Some utilities will give you lower rate for gas if you purchase higher AFUE rated equipment. For tax rebates, incentives, and credits see our HVAC Rebates and Incentives page.

Gas Furnace AFUE Definition | Annual Fuel Utilization Efficiency Comparison Chart

 Typical AFUE Numbers for Various Fuels 
FuelFurnace/boilerAFUE
Heating oilCast iron (pre-1970)60%
Retention head burner70–78%
Mid efficiency83–89%
Electric heatingCentral or baseboard100%
Geothermal heat pumpsee COP
Air-source heat pumpsee HSPF
Natural gas
Standard efficiency78–84%
Condensing90–97%
Propane
Standard efficiency79–85%
Condensing88–95%
FirewoodConventional45–55%
Advanced55–65%
State-of-the-Art75–90%

Gas Furnace AFUE and Regional Considerations and Requirements

heating fuels used by region AFUE

Official AFUE Definition:

The ratio of annual output energy to annual input energy, which includes any non‐heating‐season pilot input loss and, for gas or oil‐fired furnaces or boilers, does not include electric energy.

The Department of Energy has passed mandates that require manufacturers, distributors, and contractors to comply with regional requirement standards. The mandates requires these parties to only sell certain rated AFUE appliances based on the region. This is an effort to enhance efficiency levels of gas/oil furnaces based on the regions. The DOE released the following table for the regions/AFUE requirements. Click on the chart to enlarge.

Gas Furnace AFUE Definition | HVAC Terminology | Conclusion

If you have an older gas furnace (pre-1992) then it is very possible it is less than 80% AFUE. If it is 80% AFUE then 20% of the money you pay for gas is going up the furnace flue. Upgrade to a higher AFUE rated furnace and see your bills decrease for gas. Additionally, don’t forget the ductwork and insulating factors for your home. You want to hold the heat in the house. If you have leaky ductwork and bad doors and windows the heat is leaking out of your house.

Gas Furnace AFUE Definition | HVAC Terminology - High Performance HVAC

Gas Furnace AFUE Definition | HVAC Terminology

Resource, Learn More HVAC and About the Author

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