How To Evaluate the Lifespan of Your Furnace

All air conditioners and furnaces have a predicted lifespan, and while the right circumstances can elongate the life of a furnace, eventually — even with the best care — you’ll need to consider a replacement.

In an ideal world, you could replace your furnace at the exact moment when the cost of repairing it outweighs the cost of a brand new heater. Here’s the problem: most furnaces won’t show obvious signs of major problems before they stop working entirely — so if you wait too long, you risk finding yourself unexpectedly with no way to heat your home.

To prevent a sudden breakdown of your heater (and the resulting panicked trip to buy another furnace), here’s how you can plan ahead, and prepare to buy a new furnace as your current model reaches the end of its anticipated lifespan.

The Typical Furnace Lifespan

In most circumstances, furnaces last between 15 and 20 years — however, this average varies according to the quality of the unit, how frequently it’s used, and whether it’s properly maintained.

The longevity of your model also depends on the specific type of unit you install. Older models with heavy cast iron heat exchangers can sometimes last longer (between 30 and 40 years), although they are far less efficient. The predicted lifespan for an electric furnace is 20-30 years, while a gas furnace will last on average 10-15 years.

Remember, your furnace doesn’t run on one component alone. The average furnace — whether running on gas or electricity — works using a collection of crucial parts. Any of these parts might break or malfunction before the whole furnace collapses, because the lifespans of the components are lower than the complete furnace itself. For instance, the average life expectancy of a heat exchanger is around 15 to 20 years.

Lifespan Depends on Various Factors

The general estimates for furnace lifespan assume that the furnace is properly installed and well-maintained. If your furnace wasn’t fitted properly to your home, or isn’t cared for with regular maintenance, then it may only last for a fraction of the time expected.

Some of the factors that impact life expectancy include:

• Furnace installation — A poor initial installation could take years off your furnace’s life. Opt for professional assistance, rather than attempting the DIY route.
• Furnace size — If your furnace is too small for your home, it will overwork constantly, and therefore burn out quicker than you’d expect. On the other hand, if your furnace is too large for the space, it will experience greater amounts of on-and-off cycles — placing additional stress on the system, and causing it to wear out earlier.
• Maintenance history — Your annual maintenance efforts have a huge impact on your furnace’s life. Always schedule annual tune-ups before each heating season, as this will increase the chances of experts spotting small problems before they’re blown into huge catastrophes.
• Filter care — Keeping a fresh filter in your furnace limits airflow problems that would place additional stress on your system. Change out your filters regularly to optimize your furnace’s lifespan.
• Local climate — A gas furnace in Southern California should generally last longer with full maintenance than one in a colder climate. This is because the warm atmosphere of the area allows for less use of the system (and less wear overall).
• Energy efficiency of the system — While older, less efficient systems may last longer, they’re no longer an option for residents of Southern California, where Annual Fuel Utilization Efficiency (AFUE) standards are rising. The best option is to purchase a high-efficiency model that uses less energy to produce the same amount of heat. The AFUE rating should indicate how much energy you’ll need to use to produce a certain amount of heat.

Is Your Time Up?

Though gas and electric furnaces can both last longer than the predictions, it’s likely they will cease to perform efficiently as they near the end of their average lifespan — leading to higher energy bills for you. If your system is approaching 15-20 years in age, your bills are probably already higher than they need to be, and your system may not be as safe, or stable as it once was.

Aside from using more energy, an older furnace can develop cracks in the heat exchanger — which can become large enough to emit carbon monoxide in the case of gas models.

Your annual maintenance should give you insight as to when your furnace is approaching the end of its useful life. Don’t forget to ask your technician for guidance on whether you should think about replacing as the years go on.