Because heating homes requires a good deal of energy, the U.S. Department of Energy (DOE) has developed standards that measure furnace efficiency to help consumers select the best systems for their homes based on fuel consumption and the amount of heat the system delivers directly for heating.
Efficiency in systems that use fuel is called the AFUE, short for annual fuel utilization efficiency. The number assigned to each model actually represents the percentage of fuel the system uses that translates to heat for the home. The minimum AFUE for furnaces stands at 80, which means the system uses 80 percent of the fuel for heating. The other 20 percent of the heat the fuel creates is lost in the process, typically going up the chimney or used as a standing pilot light found in older furnaces.
AFUE ratings for the most efficient systems approach 99 percent, which indicates that nearly all the heat the fuel creates is used directly for heating. Such furnaces are called condensing furnaces because they condense the heat from the water vapor burned gas creates. They extract it with a second heat exchanger that's not found in a conventional furnace. While these furnaces are highly efficient, not all homes can be retrofit to take advantage of this technology.
Why Efficiency Ratings Matter
In a cold winter climate like ours, paying attention to furnace efficiency rating is important to lower short- and long-term heating costs. If you're considering replacing your current system, it's a good idea to consider the highest efficiency rating that you can afford, since more efficient systems utilize the heat the fuel creates better.
Choosing an upgraded furnace with an AFUE of 90 versus one with a rating of 80 will save 10 percent on monthly heating costs. Over time, those savings offset the extra cost of the system.
To learn more about furnace efficiency and your heating budget, contact Comfort24-7.com. We can help you find a trusted HVAC contractor throughout the Chicago area, and in northwestern Indiana and southeastern Michigan.