Is a 98% AFUE furnace worth it over a 96% furnace in Minnesota?
On gas savings alone, rarely: going from 96% to 98% AFUE cuts furnace gas use by about 2%, while 80% to 95% or better cuts it by about a sixth. What a 98% furnace really buys is modulating heat and a variable-speed blower, meaning quieter, steadier heat in bigger or harder-to-heat homes.
Key points
- AFUE is the share of the fuel that ends up as heat in the house over a season, measured in a lab test.
- 96% to 98% saves about 2% of furnace gas. 80% to 96% saves about 17%.
- The extra money for a 98% furnace mostly buys modulating burners and variable-speed blowers, not efficiency.
- Moving from an 80% furnace to a condensing one usually means new PVC venting, a condensate drain and sometimes a chimney liner.
- Our installed ranges: 80% furnaces roughly $4,500–$6,000, 96–98% furnaces roughly $6,500–$9,500.
On gas savings alone, a 98% AFUE furnace is rarely worth much over a 96% one: it burns about 2% less gas for the same heat. What the extra money usually buys is a modulating burner and a variable-speed blower, and in some Minnesota houses that difference in comfort and noise is worth paying for. So if you're comparing quotes and one says 96% and the other says 98%, the efficiency number is the smallest difference between them. The bigger difference is how the burner fires, how the blower runs, and how much you'll notice either one in a January cold snap. This post walks through the math with your own gas bill and then covers which furnace fits which house.
What does a furnace's AFUE rating measure?
AFUE stands for Annual Fuel Utilization Efficiency. It's the share of the gas (or propane) that becomes heat inside your house over a typical heating season. The rest goes out the vent. A 96% furnace turns 96 of every 100 units of fuel into heat. A 98% furnace turns 98 into heat.
The rating comes from a lab test run under a federal procedure based on ASHRAE Standard 103, so every brand is rated the same way. Three things it doesn't tell you:
- Blower electricity. AFUE counts fuel only. The fan that pushes air through your ducts runs on electricity, and in Minnesota it runs for months.
- Comfort. Two furnaces with the same AFUE can feel completely different depending on staging and blower type.
- Your installation. Leaky ducts in an unheated space, a furnace sized too big, or a clogged filter all cost you heat that no rating accounts for.
One more catch: brochures say "up to" for a reason. The same model line can carry slightly different AFUE ratings by size and by whether it's installed upflow or horizontal. Your exact model's rating is listed in the AHRI directory, and that listed number is what utility rebates go by.
How do you calculate gas savings from a higher AFUE?
Because AFUE is a straight percentage, you can work out the savings without anyone's sales sheet. This table shows how much gas each furnace burns to deliver the same heat, with an 80% furnace as the starting point.
| Furnace AFUE | Gas used for the same heat | Less gas than an 80% furnace |
|---|---|---|
| 80% | 100 | none |
| 92% | 87.0 | 13% |
| 95% | 84.2 | 16% |
| 96% | 83.3 | 17% |
| 97% | 82.5 | 18% |
| 98% | 81.6 | 18% |
Going from 96% to 98% cuts furnace gas use by about 2%. Going from 80% to anything 95% or higher cuts it by about a sixth. That's why the first jump pays for itself in a Minnesota winter and the last two points usually don't.
To put your own numbers on it, pull a year of usage from your CenterPoint Energy or Xcel Energy bill. Take a summer month's therms, which is mostly the water heater, dryer and range, and multiply by 12. Subtract that from the year's total. What's left is roughly what the furnace burns. Multiply that by the saving that fits your upgrade (about 17% for 80% to 96%, about 2% for 96% to 98%) and then by your all-in cost per therm, and you have a realistic yearly figure. For every 100 therms a 96% furnace burns, a 98% furnace would burn about 98.
On propane, outside the town gas lines, the percentages are the same but each unit of heat usually costs more than it does on natural gas, so every point of AFUE is worth more dollars and the math tilts a little toward the higher-efficiency furnace. Our post on propane heating costs covers the fuel side.
What comes with a 98% AFUE furnace besides efficiency?
Manufacturers put their highest AFUE ratings on their top-tier furnaces, so a 98% quote usually brings more than efficiency along with it:
- A modulating gas valve. Instead of full fire or off (single-stage) or low and high (two-stage), a modulating furnace adjusts its output in small steps. Carrier, for example, says its Infinity 98 adjusts in 1% increments when paired with its Infinity control.
- A variable-speed blower that ramps up slowly and spends most of its time at low speed.
- A communicating control on many top-tier models, which you need to get the full range of staging.
In practice that means long, quiet, low-fire cycles on the 20°F days that make up much of a Minnesota winter, with full fire held back for the -20°F nights. Rooms far from the furnace stay closer to the thermostat setting, and the blower noise at the registers drops. If quiet is what you're after, our post on quiet furnaces goes further into what makes the difference.
You can get much of that comfort at 96–97% too. Several brands sell two-stage, variable-speed furnaces in that range, and for a lot of houses that's the better value.
| A typical 96% quote | A typical 98% quote | |
|---|---|---|
| Gas for the same heat | 100 | about 98 |
| Burner | Single-stage or two-stage | Usually modulating |
| Blower | ECM, constant-torque or variable-speed | Variable-speed |
| Thermostat | Standard or smart thermostat | Often the maker's communicating control |
| Venting and drain | PVC vent and condensate drain | The same |
| Place in our $6,500–$9,500 range | Lower to middle | Upper |
What changes when you go from an 80% to a 90%-plus furnace?
If you're coming from an 80% furnace, the efficiency jump changes the whole installation. A 90%-plus furnace condenses water out of its exhaust, so it vents through PVC pipe out a side wall or the roof instead of up the metal flue and chimney. It needs a condensate drain, and direct-vent models also pull combustion air through a second pipe. If a gas water heater stays in the old chimney by itself, that chimney may now be far too big for it and need a liner. None of this is optional, and a quote that skips it isn't a real price.
Side-wall PVC also brings a Minnesota chore: keeping snow and frost off the pipes. Our guide to clearing a frozen furnace vent covers what to do when a drift or ice collar shuts the furnace down.
Rebates can tip the math. CenterPoint Energy's heating rebates require equipment listed with AHRI or ENERGY STAR and a verified AFUE, and ENERGY STAR's current furnace spec for northern states starts at 97%. So a 96% furnace and a 97% furnace can land in different rebate tiers. Programs change every year, so check the current terms before you sign. Our Xcel and CenterPoint rebate guide lists where to look.
Which furnace we'd pick for which house
These are the calls we make most often on furnace replacements:
- 96% single-stage: rentals, smaller well-insulated houses, and tight budgets where the money is better spent on something else, like attic insulation.
- 96–97% two-stage with a variable-speed blower: most Minnesota homes. It handles cold snaps well, runs quietly on low fire, and costs less than a modulating furnace.
- 98% modulating: larger or two-story homes with rooms that never quite match the thermostat, zoned systems, bedrooms next to the mechanical room, and owners planning to stay a long time.
- Adding a heat pump later: any of these can pair with a heat pump as a dual-fuel system. Our dual-fuel guide explains how the switchover works.
On price, our installed range for an 80% furnace is roughly $4,500–$6,000 and for a 96–98% furnace roughly $6,500–$9,500. Where you land inside that range depends mostly on staging, blower type and venting work, not the badge. The furnace replacement cost guide and our pricing page break it down further. In older city houses, the venting route is often what moves the price; our page on furnace replacement in Minneapolis covers why.
What to ask on every furnace quote
- The exact model number and its AHRI-listed AFUE, not the brochure's "up to."
- Single-stage, two-stage or modulating, and what kind of blower motor.
- How the furnace was sized. We use a Manual J load calculation, not the old nameplate.
- Where the PVC vent and intake will exit, and how high above the snow line.
- Where the condensate drains, and whether a pump is needed.
- What happens to the water heater's venting if the furnace leaves the chimney.
- Whether the permit and warranty registration are included.
What to do next
Before you compare quotes, get the exact model numbers and look up each one's listed AFUE. Then compare staging and blower type side by side, because that's where the real difference is. We size every replacement with a Manual J load calculation and put the price in writing before any work starts. If your current furnace is acting up and you're not sure it's worth repairing, our $79 trip charge is waived when you approve the repair. Call 612-429-3465, any day from 7am to 9pm.
Questions
Does a higher AFUE furnace heat my house faster?
No. AFUE describes how much of the fuel becomes heat, not how much heat the furnace puts out. Output depends on the furnace's BTU size and your ductwork. A properly sized 96% furnace and a properly sized 98% furnace will warm the house about the same. The 98% model, usually modulating, just does it with longer, gentler cycles.
Does AFUE include the blower's electricity?
No. AFUE only counts the fuel. The blower runs on electricity, and in a Minnesota winter it runs a lot. Most new furnaces use ECM blower motors, either constant-torque or fully variable-speed, which draw less power than the old PSC motors. That electric saving is real, but it doesn't show up in the AFUE number.
Is an 80% furnace still legal to install in Minnesota?
Yes, 80% gas furnaces are still sold and installed. We rarely recommend one in Minnesota because an 80% furnace burns about 20% more gas than a 96% furnace for the same heat, and our winters are long. It can make sense where there's no workable route for PVC venting and the chimney is lined and in good shape.
Where do I find the real AFUE of the furnace I'm being quoted?
Ask for the AHRI certificate number or the exact model number, then look it up in the AHRI directory. Brochures say "up to" for a reason: AFUE can vary by furnace size and by whether it's installed upflow or horizontal. Utility rebates go by the listed rating for your exact model, not the brochure.
Sources
- AHRI directory ahridirectory.org
- ENERGY STAR energystar.gov