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AFUE vs. AFUE: Comparing Furnace Efficiency for Denver Homes

Your furnace’s AFUE rating dictates how high or low your monthly heating bills will be. The higher the AFUE, the lower your monthly heating bills. But the downside is that higher AFUE furnaces cost more.

So, given that information, how do you decide which furnace is best for your Denver home? Does it make sense to stomach the higher upfront cost of a high-efficiency furnace in exchange for lower heating bills?

Well, it really depends on whether the long-term monthly savings outweigh the higher installation price.

We’ll show you how to compare furnaces with different AFUE ratings to ensure you pick the right furnace for your home. But first let’s take a quick look at the AFUE options available today.

What are my options when it comes to AFUE ratings?

Today, the minimum AFUE you can buy is 80% but it’s certainly not your only option. In fact, gas furnaces today have AFUE ratings as high as 98.5%.

So, what’s really the difference between a mid-efficiency furnace (80%) and a high-efficiency furnace (90% or higher)?

Well, here’s how it works: let’s say you have an 80% AFUE furnace. That percentage means that for every dollar you spend on gas, 80 cents go toward actual heat but 20 cents get wasted (heat that escapes up the flue).

Now, let’s compare that to a popular option for Denver homeowners: a 95% AFUE furnace, where 95 cents go toward heating and only 5 cents get wasted.

Over time, the savings you accumulate with a 95% furnace is pretty substantial.

But are the savings really worth it when you factor in the higher installation cost of the 95% furnace? Or are you better off going with a less expensive and less efficient furnace and just paying slightly higher heating bills every month?

Well, let’s see...

How to calculate your overall furnace savings

Let’s say that you are deciding between an 80% AFUE furnace and a 95% AFUE furnace:

Step 1: Determine the installation cost difference between the furnaces.

For this, we suggest you call several local contractors to get the average price of installation for the furnaces you’re considering.

For our example (80% AFUE vs. 95% AFUE), we’ll use the American Public Gas Association’s prices: on average, a high-efficiency furnace (95% AFUE) costs $350 more than a mid-efficiency furnace (80% AFUE) along with $1,500 to $2,000 more in installation costs.

So, we’ll assume our 95% AFUE furnace costs around $1,850 more in total than an 80% AFUE furnace ($350 + $1,500).

Step 2: Calculate how much you’d save over the lifetime of the furnace.

For this, we used an Energy Savings Calculator. Just enter both AFUE ratings to get an idea of how much more you’d save on heating costs with a higher AFUE.

For our example, this is what we found:


A furnace lasts anywhere from 15-20 years so you can see that a 95% AFUE furnace yields a lifetime savings of at least $3,306 in Colorado. But now let’s factor in the higher installation cost of that high efficiency furnace.

Step 3: Determine the net lifetime savings (subtract difference in installation cost).

If we subtract the difference in installation from the lifetime savings, we’ll get the net lifetime savings.

So, overall, by choosing a 95% AFUE furnace instead of an 80% AFUE furnace, you’ll save at least $1,456 in heating costs.

Don’t forget other factors that affect monthly prices

Your furnace’s AFUE rating isn’t the only factor that affects your monthly heating bills. In fact, if you fail to consider the following 3 factors, you could end up paying more than you should every month:

  • Getting the right size furnace
  • Quality of the installation
  • How much your air ducts leak

Need help from a Colorado Plumbing, Heating, Cooling, or Electrical Specialist? 

For your convenience, you can request an appointment in one of two ways:

  • Call us at (303) 436-2525 for immediate assistance.
  • Click on the button below to schedule your appointment online.


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