What is an 80% gas furnace?

An 80% gas furnace refers to a type of heating system that operates at 80% Annual Fuel Utilization Efficiency (AFUE). AFUE is a measure of how efficiently a furnace converts the energy in its fuel (natural gas, in this case) into heat over the course of a heating season. The AFUE percentage represents the portion of fuel energy that is effectively turned into usable heat for the home.

Here’s how AFUE is calculated: If a furnace has an 80% AFUE, it means that 80% of the energy in the fuel is converted into heat, and the remaining 20% is lost during the combustion process or through other means.

An 80% AFUE is relatively standard for older gas furnaces, and many existing homes may still have furnaces with this efficiency rating. However, newer models often have higher AFUE ratings, such as 90%, 95%, or even more, indicating greater efficiency and less wasted energy.

When considering a furnace replacement or installation, it’s common for homeowners to opt for furnaces with higher AFUE ratings because they can provide better energy efficiency and potentially result in lower utility bills. However, the choice depends on various factors, including the climate in your area, the cost of energy, and the initial investment you are willing to make.

It’s important to note that the minimum AFUE rating for newly manufactured gas furnaces in the United States has increased over the years. Current standards typically require new gas furnaces to have an AFUE of at least 80%, but many newer models on the market surpass this minimum requirement. Always check the specific AFUE rating and features of a furnace model before making a purchase decision.

Not sure what you have existing? No worries. An easy way to determine what efficiency your gas furnace is to look at the flute exhaust. If it exhausts in a metal pipe, then it is 80% efficient.