Need a new heating system? Living in Minnesota, we know the importance of having a top-of-the-line furnace to get us through those cold winter months. Efficiency is one of the most important factors you need to think about when buying a furnace. In this article, we’ll explain AFUE ratings, which is how furnace efficiency is measured. Understanding this will help you select the perfect heating system for your home.

What is AFUE?

AFUE, or Annual Fuel Utilization Efficiency, is a ratio used to measure the efficiency of your furnace. It tells how effective it is at converting fuel into energy. Higher efficiency means a higher AFUE rating, and lower efficiency furnaces will have a lower rating. For example, if your furnace has an 85 percent AFUE, it means that it converts 85 percent of its energy into heat. The other 15 percent gets used up in the heating process.

What’s considered a “good” AFUE?

Heating systems that are old or under-performing can have an AFUE that’s as low as 56 to 70%. Government standards mandate that new furnaces have AFUE ratings of 78% or higher. Mid-efficiency systems generally have AFUE ratings somewhere around 80 to 83%. Anything above 90% is considered to be a high-efficiency heating system. Since no heating system is perfectly efficient, the highest AFUE rating is somewhere around 97 percent to 98.5%.

Is a high efficiency furnace really worth it?

Well, that depends on a lot of factors. One big consideration is where you live. If you live in a cold climate, you’re more likely to save money with a high-efficiency furnace. The extra boost in efficiency can reduce your heating expenses over the course of the year.

Let’s consider an example. Let’s say your gas furnace has an AFUE rating of 80 percent. You’re considering replacing it with a high-efficiency model with a 96% AFUE rating. Since this model is 16% more efficient, it’ll end up saving you 16% each year in energy expenses. According to the American Gas Association, homeowners spend an average amount of $600 on heating expenses each year. With our more efficient heating system, you’d save 16% of this expense, which is $96 per year.


High-efficiency furnace systems are around $1,000 more expensive than mid-efficiency systems. While that seems like a lot of money upfront, consider this: The average lifespan of a furnace is about 15 years. If you save $96 for 15 years, that’ll amount to over $1,500. Although you may pay more for a high-efficiency furnace upfront, it will be worth it in the long run. However, this is especially true for folks living in colder climates, who spend more on heating their homes in the winter.

One of the best investments a homeowner can make is a quality heating system. Are you shopping around for a gas furnace or another HVAC product? Give K&S a call. You can reach our Rochester location at (507) 282-4328, or our ​Twin Cities location at (952) 697-4328. ​We’d love to talk to you about your options.