How Long Does a Furnace Last?

How Long Does a Furnace Last?
Luke Watson
Residential Sales Professional

I am a Residential Sales Professional for Fire & Ice. I provide customized solutions based on a customer’s home needs and desired comfort.

About This Article

How long will your furnace last? And what can you do to ensure it lasts as long as possible? We walk through all the steps needed to protect your HVAC investment.

How Long Does a Furnace Last?

A well-maintained modern furnace will generally last about 15-20 years before needing major repairs or replacement. However, many factors contribute to this that can extend or reduce this estimate, including maintenance, proper system sizing, properly sized ductwork, furnace brand and equipment compatibility.

We all want certainty with major purchases. Will my car last 70,000 miles or 200,000 before it starts to break down? Will my windows continue to prevent major air leaks for the next 10-20 years?

And will my furnace or air conditioner work efficiently for the next two decades of living in a home?

We’re going to focus on the furnace question today. We tell many of our customers that 15-20 years is a reasonable estimate for a properly installed and well-maintained system, and it is. But that’s an estimate, and a lot goes into that assumption. Just as importantly, a lot can happen to reduce that expectation.

Fortunately, this is where you and your HVAC partner come in. There’s no guarantee of a particular year total before you start to get hit with repairs, but there’s a lot you can do to avoid the worst of it.

Furnace burners

The Difference Between Old and New Furnaces

“They don’t make ‘em like they used to.”

You’ve undoubtedly heard this phrase. And in HVAC, it’s true. But it might not be true in the way you’re expecting.

We visit households with furnaces that are still working after 25 or even 30 years! If we stopped with that fact, it might seem like the 15-20 year expectation for modern furnaces is worse. After all, 30 years is better than 20. Right?

There are two big factors to keep in mind that will adjust this calculation:

  1. Since older systems were generally basic, single-stage units without many additional options, it was often cheaper to replace major parts for them rather than replace the entire system. So that 30-year-old furnace probably has none of the major components it was installed with.
  2. Modern systems are more efficient. Sometimes a lot more efficient. They have more options, more built-in safety precautions, will provide better comfort for your home, and will often lower your utility costs considerably.

Take those two together and the calculation shifts quite a bit. Sure, you could squeeze 30 years out of some systems if you’re lucky, but you probably don’t want to, because you’re sacrificing comfort and money in the long run. A system that’s “running fine” might actually be a money pit. But if that’s all you’re used to, it can be misleading.

The Importance of Furnace Maintenance

So I just told you I’ve seen furnaces that are 30+ years old, and that’s true. But the opposite is true as well: we’ve had to replace furnaces that are under 10 years old!

The biggest reason for this is lack of maintenance. Actually, I’ll go a step further: sometimes the only reason for this is a lack of maintenance. Think of it like your car; if you forget the oil change, it will run ok for a while, but eventually you’ll run out of luck.

And just like your car, if a system is running, that’s not enough to say that it’s running well. That’s the biggest thing maintenance provides. But it also goes beyond that.

At some point, something within your system will start to break down. This is inevitable, regardless of how well-maintained it is. From a homeowner’s perspective, this will usually seem sudden. “It was working fine and then just stopped” is a phrase we’ll hear a lot.

The thing is, equipment that’s running fine doesn’t just break down out of nowhere. There are always signs leading up to it. These issues are usually detectable months or even years in advance. You often won’t be able to see the signs just by running your system, unless there’s a loud noise or obvious drop in heat being produced. But for someone inside the system, inspecting and adjusting parts for optimal operation, they’re going to be able to see a lot more.

Static Pressure, Or Running a Marathon In a Mask

To show what I mean, here’s a simple but powerful example: Static pressure is basically when your blower motor (which moves air through your system) has to work harder than it should to move the proper amount of air through a home.

And what can cause high levels of static pressure? Let’s count:

  1. Clogged filter that isn’t allowing air to move through it smoothly
  2. Overly large filter for the system that has the same effect as a clogged filter on airflow
  3. Gunk in the blower motor itself, which makes functioning more difficult
  4. Buildup of dirt, dust and small objects in your ductwork. Have your kids ever dropped something down an air vent? That’s affecting airflow and can start to collect dirt and dust to make the problem even worse.
  5. Ductwork that’s too small. Let’s say your ductwork isn’t wide enough. That creates backups of airflow in the system. And if the ductwork is too large? The fan is working overtime just to get the air moving through it.
  6. If burners in the furnace aren’t all lighting, the fan may have to run for longer to spread heat evenly.

To put it in different terms, imagine draping a towel over your head that covers your mouth. Now try to run a marathon. How much harder will it be with that towel lodged in your mouth? Your breath in this scenario is the blower fan in your furnace, and it’s working overtime because it’s clogged up.

Most or all of these are things regular service can prevent. And, to bring us back to our central question of lifespan, it can easily be the difference between having your furnace for 10 years or 20 years.

Does the Size of Your System Matter?

We’ve talked in the past about the Manual J Load Calculation, which should happen any time you get an estimate for a system replacement. Basically, it determines what power level (referred to as “size”) a furnace should be to properly heat your home. This calculation is very important to the life of your furnace.

If Your System Is Too Small

If the power of the system isn’t enough to heat your home, this is bad for some obvious reasons. If you have a split-level home, the second story is probably never going to heat up as much as you want it to. Additionally, your furnace is going to have run almost constantly when it gets colder, to keep up with the temperatures. More run-time equates to more stress on the equipment, and more money spent each winter.

If Your System Is Too Big - Short Cycling

A system that’s too powerful is a big problem, but it’s less obvious why. After all, if your system has the power to heat your home in 20 minutes, wouldn’t 15 minutes be better?

But imagine a too-large system pumps a bunch of warm air into your home quickly. The thermostat is going to detect this and will signal for the heater to shut down. But when the air is pumped into the home too quickly, it doesn’t have a chance to properly mix with the colder air.

So if your thermostat is set to 72 degrees, the thermostat might detect 72 degrees momentarily. But as soon as the air mixes evenly with all air in the home, it will drop to 71 or 70. Then your thermostat will signal for the furnace to turn on again.

This can happen in as little as a minute. At this point, hopefully you’re starting to see the issue. The furnace will kick on, then off, then on, then off, and so on. This is known as short cycling.

A furnace that kicks on and off 20 times an hour is going to break down a LOT sooner than one that only turns on 2-3 times. And this will only happen if your HVAC system is too powerful for the home it’s in.

Inside a gas furnace

Does Furnace Brand or Model Matter?

Does the furnace brand matter? Sort of. Some people have a preference of brand, but the fact is, several well-known brands make quality HVAC equipment. We’re partial to Trane and Carrier here at Fire & Ice, which is why we’re a dealer for those brands. But if you have a Goodman, Lennox or another major brand, you’re probably going to be in decent shape as long as it’s installed properly.

The bigger difference is going to be in the sophistication of the model. All brands have lower-end and high-end equipment. Not surprisingly, some of the lower-end equipment has a shorter expected lifespan.

That doesn’t mean it isn’t good. It can absolutely still be a major upgrade for some homes, and can last for many years. But you’re getting what you pay for in terms of long-term expectations.

So a “builder grade” entry-level furnace probably isn’t going to last as long as the high-end rocket ship that has a bunch of features and options (at least on average). But that higher-end model is going to save on utilities, provide more control and comfort, and will likely last longer.

RELATED: How Much Does a Furnace Replacement Cost?

This article isn’t a buyer’s guide, but knowing your budget and setting expectations accordingly can be important when approaching the installation of a new furnace.

Why Your Air Conditioner Matters

Wait, why are we talking about air conditioning? One important reason: your blower motor.

The blower motor controls airflow for both heating and cooling in your home. Everything we said earlier about dirt buildup, clogged filters, and proper sizing applies to the air conditioning side as well. And then it can affect the furnace.

So, for example, if your air conditioner was installed at a different time and was improperly sized, it can short cycle and burn out the blower motor just like the furnace can. Then when it gets to the colder months, you’re using an overworked fan.

If your air conditioner is being maintained, is properly sized, and is as efficient as the furnace, you’re in good shape. But neglecting one is the same as neglecting both.

Warm home

The Final Word on Furnace Life

So how long will your furnace last you? Hopefully by now you realize that a lot goes into that. The best HVAC company in the world can’t guarantee a long life for your system unless you’re taking the steps to ensure you get the most out of it.

But the good news is, you have that power. If you’re looking for the best contractor to work with, check out some of the resources below to prepare yourself.

RELATED: The Complete Guide to Home Furnaces

And if you’re ready to have someone take a look at your current system, hit one of the buttons below and we’ll be glad to come out for a free replacement estimate or service visit. We’re looking forward to meeting you!

ALSO READ: 10 Things to Get Out of an HVAC Sales Appointment

ALSO READ: Top 7 Things to Look for When Choosing an HVAC Company

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