How is Furnace Efficiency Measured?

A furnace is essential in every home, especially those located in the northern regions. When selecting a furnace, it’s important to determine whether it’s energy-efficient or not, as this directly impacts your energy bills and overall comfort.

Annual Fuel Utilization Efficiency (AFUE)

When you examine your furnace, you’ll find the Annual Fuel Utilization Efficiency (AFUE) rating on its nameplate. The AFUE measures the amount of energy that is transformed into a heating output. Generally, the higher the AFUE rating, the more efficient the furnace. This is because less fuel is used to convert energy into usable heat. For instance, a furnace with an AFUE rating of 74% converts 74 BTUs (British Thermal Units) out of every 100 BTUs from the gas.

The Ideal AFUE Rating

Old furnaces typically have an AFUE percentage of 55-65%. Modern furnaces are generally more efficient, scoring 85% and above. Those with the Energy Star certificate are required to have an AFUE rating of at least 90%.

A natural gas furnace is considered efficient if it operates between 90% to 98.5% perfect AFUE. These furnaces usually feature two heat exchangers contained in a single combustion chamber. High-efficiency furnaces also include a condensing unit, which eliminates moisture before the gas is passed on to the second exchanger.

It’s common for older furnaces to have no ratings. If your furnace still uses a pilot light that requires manual ignition, you may be using a low-efficiency furnace.

What About Electric Furnaces?

Electric furnaces are rapidly becoming a popular choice. One good reason to purchase an electric furnace is that its AFUE rating is always at 100% since no energy is lost during the conversion process. However, electric furnaces are more expensive to run since electricity costs more than fuel.

Selecting a Furnace

Although a higher AFUE indicates higher energy savings, it’s not the only factor that can determine how much your energy bill is going to be. AFUE measures the production of heat but does not measure heat loss. Even if you have a high-efficiency furnace with an AFUE rating of 90% or higher, this does not guarantee that its heating will be effective.

It’s important to choose a furnace that is the proper size for your home. A smaller furnace with a high AFUE rating still won’t be able to provide adequate heating for a bigger home. It will also have to work twice as hard to reach the desired temperature, thus resulting in a decreased lifespan and lower efficiency.

The best way to select the right furnace for your home is to contact HVAC technicians. They can assist you in choosing a furnace that suits your home’s size so that you end up with a unit that always runs at its peak performance.

Wrapping Up

In sum, the efficiency of a furnace is measured by its AFUE rating. This tells you how much fuel it converts into useful heat. An AFUE percentage ranging from 90% to 97% means that the unit is a high-efficiency model, however, this shouldn’t be the only factor to consider when selecting a new HVAC.