It's Heating Up! Check out our **HOT** Summer Specials! Read More

Skip navigation


Polar Bear Air Conditioning & Heating Inc. Blog

Furnace Efficiency Ratings: What the Numbers Mean


When it comes to heating your home, you probably have two main concerns. First, you want your home to actually be warm—consistently, evenly warm. And second, you don’t want it to cost you an arm and a leg each month when your utility bill arrives. How can you keep those bills down? By having an efficient heating system.

But it can be hard to tell what the most efficient heating system would be. Furnaces do have efficiency ratings, but what do those numbers mean? We can explain so you’ll be able to make the right choice for your home. 

Annual Fuel Utilization Efficiency

The main rating system you’ll see used for furnaces is called AFUE. This stands for Annual Fuel Utilization Efficiency. The number you’ll see is a percentage. This shows how much of the energy that the system uses gets converted into heat. For example, if a furnace has an AFUE of 80%, that means that 80% of the energy it consumes becomes heat for your home.

So what happens to that other 20%? Well, the furnace vents out exhaust that is still pretty hot. So along with the gasses that need to be sent out your flue so they don’t contaminate your home with things like carbon monoxide, a good bit of heat is being lost.

Condensing Furnaces

Almost any gas furnace will have an AFUE of at least 80% these days. In order to have an Energy Star certification, it must have an AFUE of 90%. But ten percent of your heat is still being lost! What can be done to recapture the heat from that exhaust?

Condensing furnaces have a segment of the system that allows the exhaust to cool before being vented. In this way, the heat can be absorbed into air that will flow through your ducts and warm your home. The vapors in that exhaust will condense as they cool, meaning that this system also needs to have a drainage line for the condensation. But these furnaces can have an AFUE as high as 98.5%!

Electric Furnaces

The other thing to keep in mind is that all of these numbers pertain to gas furnaces. Because electric furnaces don’t need to vent exhaust, they don’t lose any warmth. 100% of the energy they use is converted directly into heat for your home! This might sound too good to be true. Here’s where it gets a little complicated.

This does mean that an electric furnace is the most efficient option for utilizing fuel. However, it might not be the most efficient option when it comes to the cost of running it. Because electricity is almost always a more expensive energy source than natural gas, an electric furnace will probably cost somewhat more to run.

Maintaining Efficiency

Whatever heating system you have, there are ways to keep it running at its peak efficiency. Most importantly, have heating maintenance done every single year. And if you do have a problem, get furnace repair in Alexandria, VA right away. Running a struggling furnace will almost always drive up your utility bills.

Contact us today to schedule an appointment or ask any questions you have about heating systems.

Comments are closed.