A Homeowner’s Guide to Furnace Efficiency Rating


Before the National Appliance Energy Conservation Act of 1987 took effect, it wasn’t uncommon for up to 40% of the heat to be lost outside through the vent. After the act, all new furnaces in the US had to be at least 78% efficient.

Choosing an efficient furnace can help you save energy and money. If you want to choose an efficient furnace, you’ll need to pay attention to furnace efficiency ratings. Let’s take a look at what a furnace efficiency rating is and how it can affect you.

What Is a Furnace Efficiency Rating?

If your furnace generates heat using a flame, it produces carbon dioxide that needs to be vented. When you allow those gases to vent, some heat also escapes in the process. An efficient furnace will allow less heat to escape and more will go to heating your home.

You can divide the annual heat output of your furnace by the annual energy it consumes to see how efficient it is. The ratio you end up with is the average fuel utilization efficiency or AFUE.

How Does Furnace Efficiency Affect You?

The Department of Energy previously required the minimum AFUE to be 78%. However, in 2007, they raised the minimum AFUE to 80% for all new furnaces. Even more recently, there have been attempts to raise the minimum level even higher.

Due to the way they work, natural gas and electric furnaces have different base efficiencies. Many electric furnaces have a 100% AFUE.

Meanwhile, natural gas furnace efficiency hovers between 78%-84%. High-efficiency gas furnaces may range between 90%-97%.

If you are interested in installing a new high-efficiency furnace or boiler, you will most likely need to install new venting and possibly also change the ventilation. This might be easy or difficult depending on the layout of your home.

How to Choose the Best Efficiency Rating for Furnace

Luckily, modern furnaces are about 80 percent efficient. You can also find high-efficiency furnaces with ratings of 90 percent or more. When you are comparing furnace efficiency ratings, you’ll need to compare a number of different factors.

You might wonder why everyone doesn’t just buy a high-efficiency furnace. Unfortunately, the cost to replace any furnace is quite high. If you want a high-efficiency one, you’ll end up paying even more.

In fact, many high-efficiency furnaces tend to cost about one and a half to two times more than a standard efficiency model. You could be looking at between $2,000 and $6,000, plus the cost of new venting.

It’s important to consider how much the furnace will cost compared to how much you’ll save on energy consumption. For example, while an electric furnace efficiency may reach near 100% AFUE, you might spend more on electricity.

In addition, think about how often you’ll use the furnace, how long you’ll live in your home, and how it’s designed and insulated.

You create a list of questions to ask your HVAC professional. They can help you compare your options to determine what level of furnace efficiency makes the most sense for your situation.

Choosing Furnace Efficiency Rating That Meets Your Needs

Understanding the furnace efficiency rating of the furnaces you are considering purchasing is critical to making the best choice for your home and wallet. Make sure to weigh all of the related factors and discuss the decision with an HVAC professional if needed.

If you found this article helpful, make sure to read our other real estate and home articles.

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