Energy Efficiency on Boilers and Furnaces

In an effort to save money, most homeowners are doing all they can to save energy. One of the biggest culprits
of energy loss, especially if you have an old system, is your furnace or boiler. It’s something that is often
overlooked, as people may think that if it is still heating, it’s working and there’s nothing to fix. However, what
they don’t see is the amount of heat that’s being lost through the chimney and other sources. Looking at your
system’s AFUE rating can help to determine the efficiency of your system. The AFUE is a percentage that
shows how much of the furnace’s energy source is converted into BTUs of heat; The higher the AFUE rating,
the greater the efficiency your system has. This number can typically be found on the cabinet or in the user

It’s important to keep in mind that the AFUE rating was determined when the system was new and perfectly
functioning. If your unit is malfunctioning, has clogged air filters, or does not get annual maintenance every
year, it’s likely that the efficiency has dropped. In fact, furnaces that miss its maintenance appointment
annually will lose on average 5% of efficiency. The ratings and equipment features listed below can help to
determine where your system stands in terms of efficiency.

Low Efficiency

Old systems may have an efficiency rating as low as 56-70% AFUE. These systems usually have a few things
in common: A heavy heat exchanger, continuous pilot light, and a natural draft. If your system is running at this
low of an efficiency, your energy bill is most likely through the roof trying to keep your house warm in the
winter. In this case, installing a new system may be the best bet to save you money in the long run.


Typically, mid-efficiency systems have an 80-83% AFUE. As of 2018, the minimum AFUE for a furnace
produced in the U.S increased to 81%. These systems often have an exhaust fan to control the flow of
combustion air and gases more precisely, and electronic ignition, and are compact in size.


With an AFUE of 90-98.5%, these systems qualify for the Energy Star label from the U.S. Department of
Energy. These systems lose little to no heat, giving you the most bang for your buck. They usually have
condensing flue gases in a second heat exchanger for optimal efficiency and a seal combustion.

Contact Al Terry Plumbing & Heating

To have your efficiency checked on your furnace or boiler, contact the experts at Al Terry Plumbing and
Heating. We can also get you a price on a replacement if we find that your efficiency is having a significant
impact on your energy bill. Fill out our contact form or give us a call today at 603-485-4205.

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