How Long Does a Furnace Last?

Frustrated by the mystery surrounding your furnace? Learn what to expect from your furnace, including lifespan and maintenance tips.
Written by Bonnie Stinson
Reviewed by Melanie Reiff
A furnace can last up to 20 years, but that’s the best-case scenario. The lifespan of your furnace depends on how well you take care of it, how you use it, the brand, and the quality of its original installation.
If you’re a homebuyer with concerns about a potential property’s furnace—or if your own furnace is starting to clink and clank—you’re in the right place. 
This article will cover the factors that affect your furnace’s lifespan. Know these, and you can make smarter choices about how to use and repair your furnace. Good furnace maintenance ensures that your home stays predictably warm!
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The average furnace lifespan

When your furnace reaches 15 years old, you should start looking for a replacement furnace. It could function for another five years but most furnaces require extensive repairs during this time. It’s better to anticipate the future and replace it first so it doesn’t fail in the middle of a cold winter.  
Be aware that the source of your furnace’s fuel impacts its life expectancy.
Oil-fueled furnaces will last longer than gas-fired furnaces. Know which type of fuel powers your furnace. This can help you plan for energy costs, lifespan, and maintenance.

Factors that reduce furnace life expectancy

Of the many factors that affect your furnace’s lifespan, some you can control. Unfortunately, some you can’t control. For example, climate, vegetation, and the layout and materials of your home all affect how hard your furnace must work—and thus how long it will last.

Furnace size

A furnace that is too large will have short cycles of turning on and off frequently. This creates more wear and tear. 
If the furnace is too small, it could stay on too long while working extremely hard to heat a too-large space. This also adds extra wear and tear and reduces overall life expectancy.
Your furnace should be the right size system for your square footage to ensure that its cycles go on and off appropriately. 

Poor furnace installation

Proper furnace installation requires someone with training. If the drainage system and fuel lines are not correctly placed, efficiency will decrease. Inefficient airflow and energy intake can lead to carbon monoxide exhaust, not to mention damaging the furnace’s inner parts. 

Lack of routine maintenance

A furnace must be maintained, like any other machine. You can follow the manufacturer’s calendar. Here are the recommended maintenance services for a furnace:
  • Clean build-up off heat exchanges, burners, and fans
  • Replace the filters
  • Balance the fans to prolong the life of its motors
An oil furnace will need more maintenance than a gas or electric furnace since its fuel is delivered by a tank. Oil furnaces also accumulate more buildup and need more frequent filter changes.
Note that furnaces in larger homes need more frequent filter changes.

Thermostat settings

68 degrees Fahrenheit is the recommended heat setting in winter for efficiency and comfort. 
If you set the thermostat too high or too low, your system must work harder to achieve your goal temperature. This effort will take years off your furnace’s lifespan.

How will I know if it’s time to replace my furnace?

Don’t wait for a catastrophic event! Here are some of the warning signs that you may need to replace your furnace.
  • Uneven temperatures
  • Noises (new or increased)
  • Blowing cold air
  • Inability to stay at thermostat’s setting
  • Increase in energy bills (a key signifier especially if you have an energy-efficient furnace)
  • Service calls and repair bills
Look for the installation date on your furnace. If you can’t find one, use its serial number to look up the model number and year. 
Another option is to call a skilled professional. They can assess the state of your furnace and let you know how long your model is expected to last.

How to extend furnace lifespan

The best way to extend your furnace’s lifespan is to change the air filter regularly per the manufacturer’s instructions. A dirty filter will suppress airflow, making your furnace work that much harder to move heat and air. 
It’s important to get your furnace maintained annually by a trained professional. Its internal components can accumulate grime which must be carefully cleaned to keep efficiency high.
Keep your thermostat settings steady at the government’s recommended temperature for the current season.
Your home works in partnership with your furnace. Keep your house well insulated to reduce thermal loss. Make sure the ductwork and windows are clean and well-sealed.

Home insurance and your furnace

Homeowners are constantly fixing things. That’s to be expected. But what about an accidental breakage?
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FAQs

A gas furnace can last up to 30 years. However, the lifespan for most furnaces is between 15 and 20 years.
Modern furnaces will last much longer than older models thanks to technological innovation. New furnaces can last 20 years with proper maintenance, especially energy-efficient models.
Look in the furnace’s manual to find the serial number, which represents the date of manufacture. If you don’t have the manual, your furnace should have a sticker label that includes the model and serial number. Google this to find its manufacturer date.
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