Are 2 Stage Furnaces Quieter? A Furnace Myth That Will Cost You Money


Are 2 stage furnaces quieter? The marketing would have you believe so. But advertising should be taken with a grain of salt. If something seems too good to be true then it probably is.

Advertisers exaggerate and distort facts for their own benefit. However, some companies may be so eager to get their hands on new customers that they may not care if they’re promoting something that isn’t true. Looking at you Big Tobacco!

But does it happen in the heating and air conditioning industry? Sadly, yes

One of the most frequent exaggerations that I hear is about the sound comparison between a two stage and single stage furnace.

DP are 2 stage furnaces quieter

Are 2 Stage Furnaces Quieter?

A new two stage furnace is slightly quieter than a new single stage furnace. But the difference is so minor that it’s not noticeable in most situations and definitely not worth the extra cost.

Comparing the sound produced by these new furnaces would be like comparing a whisper to another whisper. They’re both quiet!

In addition, the dirty little secret that’s never mentioned is when talking about the sound a two stage furnace produces, they’re only talking about it on 1st stage or low speed. Once that furnace goes to 2nd stage or high speed they are typically louder than a single stage furnace.

Do Furnaces Have Decibel Ratings?

Furnaces do not have decibel ratings. And this is one of the clues that the claim of a quieter furnace is marketing hype. The lack of any real data to back it up. If they wanted to prove these claims it would be easy enough to put a decibel rating on each furnace.

If you’re looking for a new air conditioner, you’ll find that decibel ratings are required in the specifications and engineering information of every air conditioner. The ratings are so detailed that not only is each model compared but each size in that model is rated.

In other words, the Titan Cool Master 2 ton has a different decibel rating than the Titan Cool Master 2.5 ton air conditioner. (Completely made up brand and model because I don’t like to name names)

The AC decibel ratings are required by government standards. Air conditioners can be noisy and impact your neighbors, especially if you live in an area where the homes are close to one another. Many cities even limit how high a decibel rating your air conditioner is allowed to be.

So why all this talk about air conditioner decibel ratings? To show it can be done and manufacturers are completely capable of doing it.

For furnaces, the claim is that they don’t perform decibel ratings because once inside an enclosed space (your home) the operating noise can be impacted (amplified) by too many uncontrollable factors. While this might be true, why not have ratings for comparison between furnace models so consumers would understand the difference?

Here’s why…

How Can I Find A Quiet Gas Furnace?

While there are many factors that go into having a quiet gas furnace, as a homeowner there’s only two choices you can make that will impact the noise level of a new furnace.

90% vs 80% Efficiency Differences

While two stage and single stage furnaces have little difference in sound output, that’s not the case between 80% and 90% efficient furnaces.

This is mostly caused by the 90% furnaces having a sealed cabinet or combustion chamber. This causes a natural sound chamber that prevents the sound from traveling into the home.

The open design of 80% efficient furnaces lets all the operating noises be heard by any that are close by.

Your Contractor (as long as they know airflow)

Whether the furnace is 2 stage or a single stage, the amount of air required for the gas furnace or air conditioner to operate properly will be the same. And most of the noise levels we find irritating comes from the amount of air moving through the duct system.

That’s because the sound that bothers homeowners the most is not caused by whether the furnace is two stage or single stage. It’s from improper air flow, bad duct design and equipment that is too big.

The most important aspect of any HVAC system is air flow. It’s ALL about air flow.

That’s why your choice in contractor will make a HUGE difference in how quiet your system operates. A good quality contractor will make sure your system is properly sized (which often means making it smaller), both the supply and return ductwork is sized and installed properly and then will finally make sure once the new system is installed that all settings are tuned to your unique system.

“Isn’t that what all contractors do?”, you might ask. Not even close. Based on my experience I would say 95% of contractors do nothing but replace boxes. They don’t like to fix anything or set anything up properly. Their financial model is based on taking one box out of your house and putting another in its place as quickly as possible.

This is why so many are disappointed with a new furnace after they’ve been promised such an improvement.

So how do you get a quiet furnace?

  • Choose a 90% over an 80% efficient furnace
  • Have the furnace properly sized
  • Make sure there is proper duct design
  • Pick a high quality contractor that will install and set up a furnace properly

That’s how you get a quiet furnace!

What Is The Advantage Of A Two-Stage Furnace?

Nothing really. While marketing will say that the ability to switch between two heating stages makes two-stage furnaces more efficient, it’s simply not true.

Two stage furnaces will not make your home more comfortable, are not more energy efficient and are not quieter.

The disadvantages of two stage furnaces are that they are more complicated, more likely to need repairs, more expensive to repair and more likely to need replacement in about 10-15 years.


To get a quieter furnace pick a 90% efficient furnace and look for a contractor who has experience working with air flow. It usually separates the winners from the losers.

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