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When it comes to budgeting for major household expenses, your heating system is one of the more costly items to consider. Understanding how long your furnace should last plays a significant role in how you plan for its eventual replacement. Discover the average furnace lifespan, the factors that can shorten or extend its life, and how to tell when it’s time for a new system.


The best way to begin the discussion of how long a furnace should last is by looking at the average service life. Nationally, forced-air gas furnaces last for about 15 to 20 years.

However, this is predicated on several factors, including installation, maintenance, and how you use your system. There is a lot of control you have over how long your furnace will last, if only you take the time to understand the variables and are willing to put in a little work.


One of the first variables that will affect how long a new furnace will last is when the unit was manufactured. Technology continues evolving, including the technology for heating your home. Government regulations also continue to push the industry into higher efficiency standards. This results in newer models being more efficient than older units.

The more efficiently a furnace works, the less strain it experiences while heating your home. Less strain means less wear on your system, which translates into fewer repairs and a longer service life.

When purchasing your furnace, make sure you are getting a newer model year, manufactured within the last year or two. Manufacturer-authorized companies should have the latest models from their equipment partners.


Next, it’s important you have the right size unit for your home. Both oversized and undersized units pose a risk of straining the system. Undersized systems run constantly, while oversized units short cycle. In either case, the result is excessive strain and additional wear.

Determining the right size unit for your home takes into account several factors, starting with the size of your home. Qualified HVAC professionals will consider not just the square feet of your home but also the serviceable cubic feet of air that needs heating.

Beyond that, they’ll also consider your home’s construction, including doors, windows, and insulation. They’ll account for other heat-generating appliances, how many people occupy your home, and the external environment. All of this plays a critical role in ensuring you have a system that will effectively heat your home.


You may think that installing a furnace shouldn’t be that hard, but it can make a big difference in your operating costs and service life. There’s a lot that goes into installing a furnace properly, and an issue with any of these installation areas can reduce your unit’s service life.

There is the obvious issue with improper fuel line installation, which poses both performance and safety issues. If the line isn’t installed properly, it may not pass enough fuel to the burners to produce the appropriate amount of heat.

Then there’s the connection to the ducts running throughout your home. Improper installation here would restrict airflow or leave leaks, both reducing heating effectiveness.

Finally, there’s the drainage for the unit, especially if you’re installing a high-efficiency furnace. If you don’t have effective condensate drainage, the fluid will build up and trip the sensor that prevents an overflow. An activated sensor shuts the furnace down until the condensate drains or evaporates.


Assuming you have the right-size unit and that it’s properly installed, the next most important factor affecting service life is your maintenance schedule. A furnace should receive professional maintenance every fall before the cold weather hits.

Our technicians will provide a deep cleaning, including the heat exchanger, thermocouple, and burner. They’ll also tighten mounting hardware and electrical connections. Finally, they’ll test the system and look for minor signs of inefficiency. If they find something working sub-optimally, then you’ll have the opportunity to fix it before it causes further damage. One small component not working properly can put a strain on the entire system, leading to additional repairs and a shorter service life.


In addition to professional maintenance, how you tend to your furnace filter will also play a significant role. Your furnace depends on its ability to circulate air through the system and throughout your home. Airflow restrictions cause the furnace to retain heat, causing damage to everything from electrical components to the heat exchanger.

The most common airflow restriction happens at your furnace filter when it’s neglected. How often you should change your filter depends on its size, your air quality, and how you run your system. The best plan is to check your filter monthly to see if it’s dirty enough to warrant a change. When you do check it, gently vacuum off the intake side to help extend the filter’s life and give your system an extra efficiency boost.


How you use your furnace will also affect how long it lasts. Setting your thermostat to extremely high temperatures will strain your system, especially on the coldest days.

The fan setting on your thermostat can also play a major role. Leaving it set to “On” runs the fan constantly, even when the furnace isn’t generating heat. This prematurely wears your circulating fan and reduces the life of your furnace filter.


There are signs your furnace may be nearing the end of its effective service life. Many of these factors may also indicate a solvable problem, so work with your qualified technician to determine when it’s time to replace the system.

The first sign you should consider replacing your furnace is if your current model is more than 15 years old. As indicated earlier, the average lifespan for a properly maintained unit is 15 to 20 years. By proactively planning your replacement based on your unit’s age, you can avoid replacing it in the middle of the winter as an emergency.

Next, consider how it’s running. Frequent repairs, increasing cost of repairs, and increasing energy costs all indicate it may be nearly time to replace it. You may also experience inconsistent temperatures, the system blowing cold air, or unusual noise while it’s running.


The temperate climate around the Birmingham area creates the opportunity for a more efficient heating option that will also extend the life of your furnace. When it’s time to replace your air conditioner, consider replacing it with a heat pump, which offers both heating and cooling options.

By having a heat pump and furnace, you now have a dual-fuel system. This means that when the rare extremely low temperatures move through the area, you’ll still stay warm. However, by using a heat pump during normal weather, you reduce the amount of wear on your furnace, helping to extend its service life. Additionally, running a heat pump during mild weather is more efficient than running your furnace, saving you more on your annual heating costs.

3D Air Services, LLC continues to be the trusted provider of heating and air conditioning services for people around Alabaster. Our award-winning team provides AC and heating installation, maintenance, and repairs, along with air quality and generator services. Call to schedule your consultation with one of our furnace experts to explore your new furnace options today.

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