Skip navigation

Serving The Greater
Coeur D’Alene & Spokane Area

Serving The Greater Coeur D’Alene & Spokane Area


ACI Northwest Blog

AFUE Ratings for Furnaces: What You Should Know


When you’re researching new furnaces to replace your old one, efficiency is probably one of your top concerns. This may be partly for environmental reasons to keep your carbon footprint from getting too big. But it’s also for financial reasons because an inefficient heating system will cost a lot more money to run.

Looking at the details of any furnace, you might have spotted the acronym “AFUE” and wondered what exactly it means. AFUE is a rating system for measuring the efficiency of a furnace. Knowing what rating to look for will help you choose the right furnace. Here are the details.

Annual Fuel Utilization Efficiency

AFUE stands for Annual Fuel Utilization Efficiency. It’s a ratio of the amount of fuel a heating system uses over the course of a year’s heating compared to the amount of heat it produces. You’ll see it expressed as a percentage. The higher the percentage, the more heating energy is produced by the same amount of fuel or power. Sounds simple, right? But there’s a little more to it.

Gas Furnaces

For many decades, gas furnaces tended to convert about 70% of the energy they consumed to heat in the homes they were in. This means that 30% was wasted, allowed to escape with the exhaust. This percentage did gradually improve, and chances are, if you have a gas furnace that you’re considering replacing, it’s more than ten years old and has an AFUE of around 80%.

Since then, major advances have been made. 86-90% is considered mid-range for gas furnace efficiency. Some gas furnaces, called condensing furnaces, use a slightly different system and can have an AFUE as high as 98.5. The good news is that it will be easy to find a gas furnace replacement in Spokane, WA that is more efficient than your old one. But is that the best choice?

Electric Furnaces

The AFUE rating here is very simple. Electric furnaces don’t allow heat to escape with exhaust. They operate at 100% efficiency. No energy is lost. It all becomes heat for your home. Amazing, right? But there is a catch. Natural gas and electricity don’t cost the same amount. 

Utility Costs

It would be pretty unusual to find electricity that is more affordable than natural gas in any given area. Almost always, natural gas will be the cheaper option. However, if your home is not connected to your local utility company’s natural gas lines, it would need to be connected, which is an added cost you should weigh. In some places, it might not be possible at all.

Environmental Impact

Another piece you might want to weigh is where the electricity your furnace would consume comes from. Sometimes people assume electricity is a cleaner energy source than natural gas without realizing their electricity comes from something like a coal plant. On the other hand, if you have solar panels, electricity would definitely be the greener option.

If you have specific questions about how to weigh these factors in considering what furnace to get for your home, a member of our team would be happy to help you get answers.

ACI Northwest is here to help. Contact us today with any questions about furnace efficiency.

Comments are closed.