Are Single Stage Furnaces More Reliable? Quick Guide To A Good Furnace


These days the push for more complicated furnaces is becoming more common. This is leading to heating and air conditioning equipment that is less reliable, more expensive to repair, more difficult to repair and will have a much shorter lifespan.

But is that true with all new furnaces? Are single stage furnaces more reliable?

I’m a firm believer in KISS. KISS is most often used as the acronym for keep it simple stupid. But I’ve heard other versions.

It applies well when talking about furnaces. Especially since it’s a design principle. The most formal definition of KISS states that “most systems work best if they are kept simple rather than made complicated; therefore, simplicity should be a key goal in design, and unnecessary complexity should be avoided”.

If only HVAC manufacturers had to follow that principle.

DP are single stage furnaces more reliable

Are Single Stage Furnaces More Reliable?

Yes, single stage furnaces are more reliable. Despite the marketing that is used to push more expensive furnaces, a single-stage furnace, with its simpler and more reliable design, is the best option for the vast majority of homes.

Why Are Single Stage Furnaces More Reliable?

Edsger Wybe Dijkstra was a Dutch computer scientist. He had a lot to do with the device you’re using to read this article. In a paper he wrote in 1975, there was a handwritten notation: “Simplicity is prerequisite for reliability”.

Funny side point…Edsger lived that philosophy too. Despite having a part in modern day computing, he was known to have no use for word processors. He was a pen and paper man. Can’t get much simpler than that. Hat’s off to you professor.

I think Edsger would have liked single stage furnaces. They have a simplicity to them that leads to a more reliable central heating system within a home. 

Maybe you’re old enough to remember your parents or grandparents talking about the furnace they had since the house was built. Maybe that furnace was over 50 years old. The main reason for the long life of those style furnaces was simplicity. Old style furnaces only had 4-6 parts in them. And all of those parts were relatively inexpensive, universal and easily available.

A single-stage furnace today, while not as simple as a furnace from 50 years ago, does maintain some of those characteristics.

Most furnaces today, whether single stage, two stage or modulating have many of the same parts. The difference is the single stage furnace parts are a less complicated version.

Because of this they are more reliable, less expensive and in many cases can even be replaced by a universal part rather than having to only get it from the original equipment manufacturer. And that last point can be a big deal.

When a manufacturer makes a part that is unique to their furnace, when that part fails you will be at the mercy of that manufacturer to get that furnace up and running again. If that manufacturer is having supply issues or if it’s past the seven years that they are required to support a piece of equipment (a requirement only in some states) you might not be able to repair it at all.

I know that thought is scary enough that some will wish they never got rid of those 50 year old beasts. But let’s be practical. I mean, at some point a company has to sell enough furnaces to stay in business. And one to two furnaces in someone’s lifetime probably won’t do it. I haven’t run the numbers but I’d say it’s a pretty good guess.

In addition, there comes a time when the need to reduce our use of natural resources outweighs the costs from furnace replacements. We can’t keep using energy wasting equipment. But we don’t have to overly complicate a heating system either. Let’s stick with equipment that is overall less likely to malfunction.

Are Single Stage Less Efficient Than Two-Stage Furnaces?

This one really burns me up. It’s probably one of the most common mistruths that HVAC sales people spew. Homeowners are misled by being told that single stage furnaces are older in design and less efficient than two-stage.

Despite how often it’s said in homes and written on the internet, two-stage furnaces are NOT more efficient than single-stage furnaces. And two stage furnaces are rarely worth the extra money.

Spending less money on your gas utility comes down to the efficiency of the furnace. And the amount of gas a furnace uses is determined by the heat exchanger design. A single stage or two stage furnace of the same efficiency uses the exact same heat exchanger.

To be fair, this mistruth comes more from contractors and sales people than any manufacturer. Look closely on a manufacturers website or in their marketing literature and you’ll see that their single stage models and two stage models show the EXACT same efficiency.

In other words, a 95% efficient furnace is 95% efficient whether it’s single stage, two stage or modulating. No savings on energy bills.

And even if a manufacturer shows a 1% difference between those two models (which a couple do is extremely suspect) very small savings would be right out the window the first time the two stage furnace needed a repair.

How To Keep ANY Home Furnace More Reliable

Maintenance is important for almost any type of system. If you didn’t get an oil change every few months, imagine how bad your car would be. As bad as using old, dirty oil can be for your car, using an unmaintained heating system can be just as damaging to your furnace.

The best way to ensure that your furnace is as reliable as possible is by having regular maintenance performed. This includes cleaning filters, checking the venting system for corrosion or leakage to prevent carbon monoxide leaks, the heat exchanger needs to be inspected and electrical wiring needs to be checked just to name a few.

If you are not comfortable performing these tasks yourself then we recommend calling in a professional. In fact, some aspects of furnace maintenance need some expensive special tools that most homeowners will not own.  

A really dirty furnace filter causes the system to work harder to keep your home heated. The unnecessary wear and tear can damage the equipment and shorten its lifespan by almost half.

But if you’re not worried about how long a furnace will last.

Maybe you don’t plan on staying at your house long enough so you’re not worried about making a furnace last 20 – 30 years. Or the savings in monthly heating costs isn’t enough to convince you to drop dollars on “just maintenance”.

Regular maintenance helps avoid expensive repairs by preventing them from happening. For example, one common cause of furnace breakdown is a dirty fire sensor. A thorough heating system tune up performed by a certified HVAC technician should always include checking the flame sensor.

It’s important to get furnace maintenance done regularly. They keep furnaces running safely and efficiently, which helps them last longer and saves homeowners money on their utility bills. If your heating system is new or old, you should definitely get an inspection from a professional HVAC company or set up a reminder to have one every year.

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