4 Things That Dictate The Cost Of A Gas Furnace

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Understanding Which Features Have The Greatest Impact On The Cost To Replace A Gas Furnace

If you’re shopping for a new furnace, then you may be wondering why nearly every heating contractor in Denver acts like the price to install a new furnace is a matter of national security. There are basically 2 reasons heating contractors won’t give you any info about their furnace prices over the phone:

Reason #1

They want you to meet with a salesman who has been trained extract the maximum price he charge you based on how informed you are about the cost to install a new furnace.

Reason #2

The truthful answer to exactly how much it will cost to replace your gas furnace is… It depends. It depends on what is required to complete your installation.

sketchy ac salesman

In my opinion, reason #1 is why most people find the process of buying a new furnace so frustrating, and reason #2 is really just an excuse to justify reason #1.

There’s simply no reason Denver heating companies can’t discuss ballpark ranges for prices on new furnace installation with customers, as long as they make it clear what things are included in the basic price, and what types of things would be an additional cost. I want to give you brief overview of the 4 variables that will dictate the price of a new furnace, and roughly how much each one affects the price of a new furnace here in Denver.

  1. Efficiency
  2. Variable-Speed
  3. Single-Stage vs. 2-Stage
  4. Size (BTU’s)


Do you want an 80% efficient furnace, or does it make financial sense for you to install a high-efficiency furnace? (Furnaces with a rating of 90% or higher are referred to as high efficiency units) If you do want a high-efficiency furnace, you’ll have to decide if you want one that’s 92%, 95%, or 98% efficient.

Cost Implications of Efficiency: You can expect to spend $1,800 – $2,000 more to go from an 80% efficient furnace to a 92% efficient furnace. To upgrade from a 92% furnace to a 95% efficient furnace will cost another $1,000 – $1,200. The top-of-the-line 98% efficient furnace will set you back from $1,500 – $2,000 more than a 95% efficient furnace.

Note: 92% efficient furnaces are usually only single-stage, and do not have variable-speed fans. 95% and 98% efficient furnaces are typically going to offer 2-stage heating as well as having variable-speed (or modulating) fans, so the cost differences are not solely due to the increase in efficiency.


Do some parts of your house stay warmer or colder than others? People in the heating and air industry often referred to this as having ‘hot spots’ or ‘cold spots’ but that’s not a very accurate way to describe the problem.

If you do need to try and even out temperature differences in rooms that stay hotter or colder than others, you’ll definitely want to consider a variable-speed furnace. If you decide to go with a variable-seed furnace, you’ll also get 2-stage heating as a package deal since most of the top manufacturers include the 2-stage feature in their variable-speed models.

Cost Implications of Variable Speed: Since variable-speed furnaces are almost always going to be 2-stage as well, I will address the cost implications of both features together below.


A single-stage furnace is either off or on. Simple as that. Just like a standard lightbulb. When the furnace turns on, it’s at 100% of its capacity or output.

When a 2-stage furnace starts up, it is typically at only 2/3 of its capacity or output. It will ramp up to 100% output when the additional heating capacity is needed.

Cost Implications 2-Stage: When choosing among 80% efficient models, you will spend $1,200 – $1,500 more for a 2-stage variable-speed furnace than for a single-stage unit. In the high-efficiency category, a 95% efficient 2-stage variable-speed furnace costs between $1,000 – $1,200 than a 92% single-stage unit.

Size Of The Furnace

The size of the furnace you need depends on the size (in square feet). and energy-efficiency of your house. The bigger your home, the bigger the furnace you’ll need. Bigger furnaces are more expensive. Simple enough?

Special Note: I’ve met with customers who have worked themselves up into a giant ball of stress because they’ve gotten quotes from 2 or 3 companies, and each company told them they needed a different size furnace.

The size of the furnace you need should not be your concern. Sizing the unit properly is the job of the company you choose to install your new furnace. For example, you should expect a written guarantee that states the new furnace will heat your house to at least 68 degrees when the temperature is zero degrees outside. Any company that won’t guarantee the heating performance of your new furnace should be crossed off your list.

Cost Implications of Furnace Size: The size of the unit you need actually has a much smaller impact on the price of a new furnace than the efficiency, and variable-speed fan do. The price difference between the smallest and the largest furnaces of each type is usually no more than $200 – $700, with the larger cost differences coming on the more efficient variable-speed models.

Those are the four things that will dictate the cost of a new furnace here in Denver, and anywhere else for that matter. There are other variables that are related to your home (like code upgrades for example) that will affect the cost to install a new furnace, but the four listed above will dictate the price of the new furnace itself.

If you’d like more detailed information on furnace efficiency, the benefits of variable-speed furnaces, and single-stage vs. 2-stage furnaces you can find everything you’d ever want to know in the Furnaces 101 section of our website.

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