80% vs. 92% Furnaces: Where and Why

One of the most recognized and least understood differences in furnaces is efficiencies. I believe that there is a place for both the 80% and the 95% furnace, but as you will see below, we can make a pretty good case to never put in another stand alone 80% furnace again. Also, while I do sell this stuff for a living and stand by the Built Green philosophy, I am also a realist. I understand that it just may not be every ones cup of tea or in every ones budget.

The best thing is that we know our options, so, in this article I want to break down the different types of furnace efficiencies and what the mean to you, the contractor, and the homeowner.

Click on the 80% or 90% title to go furnace literature.

80% AFUE Furnace
(for every $1.00 spent on fuel $.20 is wasted)

The 80% efficiency is the minimum efficiency for new installation of a furnace. While many contractors have upgraded their spec install to 92% furnaces, the 80% furnace is still sufficient for most homes being built with Natural Gas as the fuel source. One of the weaknesses of the 80% furnace is that you have to vent it straight up, limiting where it can be placed or requiring special chases up through the conditioned space of a home.

Warning: The one place that an 80% furnace does not belong is in the Propane application. If you are building a custom project and the homeowner decides to use an 80% furnace, always get a quote in writing from your heating contractor that let’s them know what the upgrade to a 92% furnace would cost. When they start screaming about the energy costs in their new home, you can show them that they were given the choice to upgrade. If they had the option and did not choose it, you are off the hook.

The only thing left is to educate them on the differences and since studies show that they will hold your opinion higher over even their best friends’ when it comes to their new home, right here seems like a good place to start.

Best Scenario for the 80% Furnace: Spec homes supplied by Natural Gas with Garage Installation

95% AFUE Energy Star Furnace
(for every $1.00 spent on fuel $.05 is wasted)

The 92% efficiency is starting to become more and more standard as many start to make either a personal choice to reduce the amount of fuel and energy they consume or they just do the math and figure spending the money up front to save much more over the life of the furnace is worth it. It is not too far off that we may see the new minimum efficiency bumped up to 95%.

Here are some of the differences between the 80 and the 95. By upgrading to a 95% furnace on a 2,200 square foot home; the homeowner will save approx. $350 per year on Natural Gas or $500 per year on Propane*. These types of savings are equivalent to not driving 104,000 miles or planting 500 trees. With the cost of upgrading at around $500-$600, it kind of makes you go hmmmmm. Cascade Natural Gas also rebates $150 for the installation of a 90%+ furnace.

Best Scenario for the 90% Furnace:Custom Homes supplied by either fuel type or Spec Homes supplied by Propane. Applications where horizontal venting is required or preferred.

NOTE: Something to keep in mind is that with today’s propane prices it costs the same amount to heat a 2,200 square foot home with a 95% Propane Furnace as it does to do the same with an Electric Furnace! The solution? Heat Pumps.

Until then, feel free to call me for any reason. As well, please write with your questions, they may make great discussion for this site! - Wes

*All savings estimates are in no way exact or binding figures.