Confused About Furnace Efficiency Ratings? Here's Your Expert Guide

If you're in the market for a new furnace, one of the first things you'll encounter are furnace efficiency ratings. These ratings tell you how much of the fuel the system uses that goes directly into your home as heat and how much the furnace wastes. There's a close relationship between the ratings and the size and price of the furnace you need for your home.

The efficiency ratings for gas furnaces are called AFUE (annual fuel utilization efficiency). The minimum starts at 80 which means that the furnace uses 80 percent of the fuel it consumes for heating your home and it wastes 20 percent of the gas up the chimney or elsewhere. Systems are available with AFUE ratings as high as 99 percent, indicating they waste a mere 1 percent of the fuel they use.

Furnaces whose AFUE ratings are over 90 are usually condensing furnaces and they use a second heat exchanger to extract the heat from the water vapor burned gas creates. These systems have a slightly different configuration than the normal gas furnace and a higher price tag, but their efficiency promises significantly lower energy bills for years to come, offsetting the cost. Some units provide up to 98% efficient capabilities!

Mid-range furnace efficiency ratings have AFUE ratings in the mid-80s and if your home won't easily accept a condensing furnace, such a furnace is likely to provide you with higher efficiency than your current system offers. Some of these use two-stage heating, an energy saver when temperatures are milder and your home's heating needs are lower.

The size you need and the AFUE rating are related. Since a furnace with a higher AFUE puts out more heat, you may not need as large a system, which generally costs less. The HVAC contractor you work with should perform a load calculation using Manual J and S, both of which take into account the variables in your home that contribute to the system size you need.

To learn more about furnace efficiency ratings, contact the pros at Air Assurance, providing outstanding HVAC services for homeowners in the Broken Arrow area since 1985.

Our goal is to help educate our customers in the Tulsa and Broken Arrow, Oklahoma area about energy and home comfort issues (specific to HVAC systems). 

Image courtesy of Shutterstock

Condensing Furnaces Raise The Bar For Efficiency

If you're in the market for a new furnace for your Broken Arrow home, consider a high-efficiency condensing furnace. Furnace efficiency is measured by its annual fuel utilization efficiency, or AFUE. Furnaces older than ten years have an AFUE of up to 65 percent, which means that 65 percent of the fuel burned by the furnace is transferred to heat for your home. The remaining 35 percent is vented outside as exhaust. Condensing furnaces have an AFUE of at least 98 percent, making these units highly efficient, saving you money on energy costs.Condensing furnaces have several features that contribute to their high efficiency. Among them are:

• Dual heat exchangers. Unlike a conventional furnace, a condensing furnace has a secondary heat exchanger that recovers the exhaust from the first and uses it to heat more air for your home. The result is that more fuel is transferred to heat and less is sent up the chimney.

• Modulating gas valve. The gas valve in a condensing furnace modulates the flow of fuel to the unit from 40 to 100 percent to meet the real-time heating needs of the home. This means that during warmer periods, less fuel is burned by the unit.

• Variable-speed fan blower. A conventional furnace has two speeds: on and off. The multiple-speed fan in a condensing furnace enables it to slow the blower during warmer periods, using less electricity and keeping your home more comfortable.

• Electronically-commutated motor (ECM). A standard furnace utilizes a split-capacitor motor to run the fan. These motors can use as much electricity as a refrigerator to operate. ECMs, which are sometimes offered on condensing furnaces, are not only quieter, but also use 75 percent less electricity.

Condensing furnaces are more expensive than conventional furnaces, but their efficiency results in considerably lower utility bills. A condensing furnace will more than pay for itself over its lifetime.For more expert information about condensing furnaces, please feel free to contact us at Air Assurance, serving Broken Arrow and the Tulsa metropolitan area since 1985. Our goal is to provide the best possible service to our customers.Our goal is to help educate our customers in the Tulsa and Broken Arrow, Oklahoma area about energy and home comfort issues (specific to HVAC systems). Image courtesy of Shutterstock