What Are The Ratings For Furnace Efficiency?

When it comes time to purchase a new furnace, it’s important to consider efficiency ratings. Energy efficiency refers to how much heat is actually produced by a particular furnace, as compared with how much energy is lost in the production process. When a furnace has a low efficiency rating, you’ll be paying for wasted energy that doesn’t turn into actual heat.

You will also want to consider the type of fuel the furnace requires, and how much that fuel costs. For example, electric furnaces are very energy efficient in terms of output, but the electricity itself can be quite costly.

How to Measure Furnace Efficiency

Manufacturers use the Annual Fuel Utilization Efficiency rating (AFUE) to qualify a furnace’s energy efficiency. The rating lets the buyer know how much heat a furnace will actually produce as compared with the amount of energy that is required to produce that heat. For example, a furnace that is rated at 80 percent AFUE has a 20 percent energy loss, while 80 percent actually becomes heat.

Ductwork doesn’t affect the rating, because each home’s ductwork varies, but it can factor into potential energy loss. Ductwork that runs through attic spaces, for example, can lose as much as 35 percent of the system’s heating efficiency.

When an Older Unit Doesn’t Have a Rating

New furnaces have AFUE ratings, which is required by the Federal Trade Commission. Older systems may not have this rating, or it may have been removed, since the requirement is relatively new. The following guidelines can give you an estimate of your current furnace’s energy efficiency.

Low-Efficiency Furnaces—These furnaces have a continuous pilot light that must be relit if it goes out. The furnaces work by gravity, with heat naturally rising and drafts naturally distributing the produced heat. Some low-efficiency furnaces have blowers installed, which can increase the efficiency. However, the units can still be recognized by their octopus-style ductwork. Low-efficiency furnaces are usually between 56 and 70 percent efficient.
Mid-Range Furnaces—With these models, a fan controls airflow. These furnaces don’t have a pilot light, as they instead use an electronic ignition. Mid-range furnaces are about 80 to 83 percent efficient.
High-Efficiency Furnaces—The condensing units in high efficiency furnaces first remove water from the exhaust gas, and then send that gas through a second heat exchanger for added energy efficiency. The combustion units for these furnaces are sealed, and they are about 90 to 98.5 percent efficient.

ACS Air Conditioning Systems installs and repairs a wide range of energy efficient furnaces. Call us for a free estimate, and you’ll be sure to find the perfect furnace for your home.

Jennifer P.