What Furnace Efficiency Ratings Really Mean

How do you tell one furnace apart from another? Like every other appliance inside your home, selecting the wrong furnace can cost you each month. 

Take a look at a furnace, and you’ll discover they each come with a different efficiency rating. But what do furnace efficiency ratings really mean? 

The National Appliance Energy Conservation Act of 1987 established minimum efficiency standards for many common household appliances. Furnaces from that point forward used an AFUE rating scale – also known as Annual Fuel Utilization Efficiency. 

As you shop for new furnaces, you’ll find each AFUE number displayed as a percentage. With today’s equipment, you’ll most likely find ratings between 50 and 100 percent. The higher the number, the more efficient the furnace. It should be clearly posted on the front faceplate of the furnace. Or look it up through the unit’s serial number. 

This AFUE rating tells you how much of the fuel used for the furnace is converted into energy, and how much of it is lost. If a furnace has an 85 percent AFUE rating, that means it converts 85 percent of the fuel into heat, and loses 15 percent in the combustion process. 

Where does this excess heat loss go? It may be misdirected into your attic or crawlspace. It may flow directly through your roof to the outside. In the above example, this equates to a 15 cent loss for every dollar spent. That can really add up each month on your utility bill, and over the life of your furnace. 

Furnace efficiency ratings are for furnace equipment only. They don’t take into effect other energy problem areas throughout your home, including ductwork, insulation, doors and windows, or a drafty attic. 

While guidelines suggest a well maintained furnace can last 15 to 20 years, it’s not uncommon to find home furnaces beyond 20 years. The National Appliance Energy Conservation Act set AFUE standards to 78 percent through 2015, then moved it to 80 percent after. To earn an EnergyStar rating, today’s furnaces must exceed 90 percent AFUE. 

That can be huge savings on your overall utility bill each month.

Want to learn more about efficiency? An energy audit will help you discover where you can make improvements that will have a big impact on your monthly expenses, plus make your home more comfortable in the process. Give us a call today.