What Is AFUE and Why Should I Care?

If you’ve been shopping for a furnace, chances are you’ve noticed that each furnace has its own annual fuel utilization efficiency (AFUE) rating. These generally range from 80% to the high 90% s and the higher the number, the more fuel efficient that particular furnace is.

But what does this number really mean and just how much should you care? Well, the AFUE rating should actually have a significant impact on your furnace purchasing decision, but that doesn’t mean that you’ll always choose the furnace with the highest efficiency rating either.

For one thing, you’ll have to recognize that not every type of furnace is capable of running at the highest efficiency levels. Oil furnaces, for instance, can’t compete with the super high efficiency gas furnaces on the market today. That’s not to say that an oil furnace might not be the best choice for you under certain circumstances, but it does mean that you should take a close look at your furnace usage before you make a decision.

If you do choose a gas furnace, you will of course have the option of getting one that can reach up to 97% or so efficiency. However, that may not always be the best choice either. If you live in a place where with very harsh, long winters and you’re going to be using your furnace heavily, then it’s definitely worth investing in a higher AFUE furnace that can save you considerable amounts on your monthly heating bills.

But if you don’t use your furnace too often as your area has more mild winters it’s probably not worth it for you to invest in such a high efficiency product. That’s because the higher the AFUE of the furnace, the more expensive it is to purchase and install. Certainly you’ll save money every month because you’ll be getting more heat out of the fuel you’re paying for. But if you don’t use your furnace all that much, the savings really won’t be that substantial.

Don’t forget that a furnace with an 80% AFUE rating is still quite energy efficient. And once you get up that high, you have to use your furnace a lot for the difference between 80% and 90% to really become apparent. So if you don’t use your furnace heavily during the winter, it will take you many, many years to make up for the higher purchase price of the 90+% AFUE models.