How Long Does a Furnace Last? Tips on How to Maintain Your Furnace

Caroline Gilbert
Written by Caroline Gilbert
Updated October 23, 2021
Young mother draping coat over her daughter’s shoulders inside their home
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Furnaces last 15 to 20 years on average—here’s how to get them through their teenage years

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If you’ve found yourself wondering how long a furnace lasts, you likely either just bought a new home or had to perform some maintenance on your current heating system. Either way, you need to know the average furnace life expectancy so you can budget for a replacement (new furnaces can cost a lot of money). So how long should it last and what can you do to extend its lifespan? 

Average Furnace Lifespan

The average gas furnace in a home lasts 15 to 20 years, though some can last 30 years or more. 

Average Life Expectancy by Furnace Type

According to the latest Residential Energy Consumption Survey from the U.S. Energy Information Administration, gas furnaces are the most common, followed by electric furnaces. Less common are oil furnaces, which tend to be used in very cold regions of the United States, though still less frequently than gas furnaces. 

  • Gas furnace: 15-20 years

  • Electric furnace: 20–30 years 

  • Oil furnace: 15–20 years, though they can last up to 25 years 

Factors That Affect Furnace Life Expectancy

The type of furnace you have isn’t the only thing that will affect its lifespan. Here’s what else can influence how long your furnace lasts: 

1. Size

Furnaces that are both too small or too large for your home can wear down faster. A furnace that is too small can struggle to heat your home, frequently staying on to try to combat the cold air. This can overwork the equipment and cause parts to degrade faster than normal. 

A furnace that is too large, on the other hand, will turn on and off too quickly. This frequent cycling also causes parts to degrade faster than normal. 

Bottom line? It’s important to hire the right HVAC technician to ensure you get a furnace that fits your home. 

2. Installation

It’s also important to hire an HVAC technician that you trust to ensure that things are installed properly. Otherwise, you may have issues like poorly installed, sized, or sealed ductwork, resulting in a loss of air pressure. Or the wrong drainage system for the type of system you have. 

You can even have serious problems with bad wiring, which can drain power or become a fire hazard, or incorrectly installed fuel lines, which can result in dangerous gas leaks. 

3. Type of Heating System

Do you have a single-stage, two-stage, or variable-capacity gas furnace? The type of system you have can affect how long your furnace lasts, so here’s what to know: 

Single-stage furnace

  • Thermostat calls for heat, furnace turns on and runs until it reaches the thermostat temperature, then shuts off 

  • Runs at 100% capacity when it’s on, which means it wastes energy

  • Less even heat

  • Most affordable and costs less to repair

  • Less likely to break

Two-stage furnace

  • Has two levels of heat output—high for the coldest days and low for everything else (usually 80% of the time, it runs on low)

  • Typically runs at 65%–70% capacity to save energy

  • More even heat 

  • More expensive than single-stage and may have slightly higher repair costs

  • Less likely to break

Variable-capacity (aka modulating furnace, aka multi-stage furnace)

  • Indoor blower motor moves at various speeds for precise heat control  

  • Can run as low as 40% capacity to save even more energy

  • Most even heat out of the three 

  • Most energy savings 

  • More expensive than both single- and two-stage furnaces with average to high repair costs

  • May be more prone to break because it uses a computerized blower motor chip that monitors airflow inside your home 

Note: If you have an older furnace, you likely have a single-stage furnace that ​​has a single heat exchanger and an energy efficiency of 80% AFUE (annualized fuel utilization efficiency). Upgrading to a 90% to 95%+ high-efficiency furnace with two heat exchangers can offer significant energy savings, even if it’s a one-stage system. 

4. Thermostat Temperature

Keeping your thermostat set too high or too low can shorten your furnace’s lifespan. The optimal range is between 60 degrees Fahrenheit and 80 degrees Fahrenheit. 

5. Maintenance

A lack of regular maintenance can also negatively affect your furnace’s longevity. 

Tips for Maintaining Your Furnace

Senior man changing out his dirty furnace air filter
Photo: steheap / Adobe Stock

To ensure your heating system lasts as long as possible, there are a few important furnace safety tips to follow and key things you should do:  

  • Change your furnace filters at least once per season—a dirty filter can block airflow and overwork the motor. 

  • Have an HVAC technician perform an annual furnace tune-up and inspection in the fall.

  • Make sure all your vents in the home are open and clear to prevent it from overworking.

  • Vacuum up any dirt or debris from floor registers. 

  • Seal any leaky ducts with special metal tape.

  • Make necessary repairs as soon as possible. 

Signs You Should Replace Your Furnace

If your furnace is entering its twilight years, you’re probably wondering when it needs to be replaced. While it has likely experienced common signs of furnace trouble in its old age, such as not producing heat, there are a few warning signs that indicate that it’s time to replace it rather than repair it: 

  • Frequent service calls

  • New or increased loud noises: ratting, banging, popping, screeching 

  • Won’t stay at the thermostat’s temperature setting

  • Blows cold air 

  • Noticeable increase in energy bills

A local HVAC professional near you can confirm if you need a replacement, advise you on which type of HVAC system is best for your home, and provide quotes. 

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