Efficiency ratings reflect how much of the fuel you pay for is actually used to heat your home. An 80% efficient furnace uses 80% of the gas to warm your living space, while the remaining 20% escapes through the exhaust system. That means for every dollar you spend on gas, only 80 cents go toward heating—while 20 cents are lost as waste.
Key Differences Beyond Efficiency
Aside from fuel usage, one of the biggest differences between these two types of furnaces lies in how they're vented and installed.
An 80% efficient furnace vents exhaust through a metal flue, usually shared with your home’s water heater, and is typically routed through the roof.
A 90%+ efficient furnace, on the other hand, uses a PVC (plastic) exhaust pipe. This is necessary because the small amount of gas released creates condensation. That moisture collects in the venting and must be drained through a floor drain, or pumped to a nearby exterior outlet. The venting on a high-efficiency unit can run through the roof (vertical venting) or out the side wall of your home (horizontal venting), offering more installation flexibility.
What About Cost?
A high-efficiency furnace typically costs about $600 to $800 more than an 80% model, depending on the brand and installer. However, many utility companies, furnace manufacturers, and even federal programs offer rebates that help bridge—or even eliminate—that price gap for 90%+ models.
If you're considering a new furnace and want to understand which efficiency level is best for your home, contact the professionals at Blue Best Plumbing, Heating, Air, & Generators. We’ll walk you through your options and help you take advantage of any rebates available along the Wasatch Front.
