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The energy efficiency rating of your furnace and what it means

Furnace, Furnace and Heat Pump Updated: November 24, 2021

According to the Department of Energy (DOE), heating your home uses more energy than any other household system—up to nearly 29% of your utility bill! That’s why it’s important to know the efficiency rating of your furnace. High-efficiency furnaces use less fuel to heat your home, making them ideal for people who live in colder climates. Below is a guide on how to find your furnace’s energy efficiency rating, what the rating means, how the rating affects your home and how to tell if you need a new furnace.

What are energy efficiency ratings?

The efficiency of a furnace is determined by a ratio called Average Fuel Utilization Efficiency (AFUE). The AFUE is a percentage found by dividing the total heat output by the unit’s total energy input. The minimum AFUE of a furnace is 80%, and a high-efficiency furnace is 90¬% or greater. The higher the AFUE, the more efficient it is.

How to find your furnace’s energy efficiency rating

Locate the AFUE on the bright yellow label located on the outside of the furnace. This label will also tell you if the furnace is high efficiency. An AFUE of 90% or above is considered high-efficiency and the minimum standard for a new furnace is 78%.

If there is no yellow label, you can locate the model number on the sticker attached inside the cabinet. Look up the model number on the manufacturer’s website to get the AFUE.

You can also determine the efficiency just by looking at the unit. A high-efficiency furnace has either one or two PVC pipes for combustion air and exhaust, while a standard efficiency furnace has a metal flue that vents exhaust to the chimney or roof.

What the rating means for the health of your home

While high-efficiency furnaces can cost more initially, they can help you save utility costs over time. In addition to energy savings, comfort is another factor. Some high-efficiency furnaces feature modulating speeds so that the flame setting can change in small increments. This means the temperature of your home will more accurately reflect the setting of your thermostat. Finally, a high-efficiency furnace means more of the gas is converted into heat, which translates to fewer greenhouse gasses being emitted into the environment.

When to replace your furnace

It’s a good idea to pay close attention to how well your furnace is operating and not delay repairs or replacement, if possible. Emergency replacements can be costly and stressful, especially if your furnace decides to call it quits in the middle of winter. Regularly check for dust, rust, cracks or corrosion around the furnace. Monitor for interruptions of warm air from your registers in the winter. Brief periods of cool air can indicate something is not working correctly within the furnace.

If your heating bill is larger than usual or the humidity in your home has increased, this could mean repairs or general maintenance is needed, but if these signs of wear and tear build up, it could be time for a replacement.

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Upgrade your furnace

You may qualify for an Energy Trust incentive.

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