Sizing starts with a Manual J, not the old nameplate
The furnace coming out of your basement tells us what someone installed 20 years ago. It doesn't tell us what the house needs now. Since then you may have added attic insulation, replaced windows or finished the basement, and the original may have been oversized to begin with.
A Manual J load calculation works it out room by room: wall and ceiling insulation, window area and type, air leakage and which way the house faces, all figured against a Minnesota winter design day. The result sets the furnace's heating capacity. We also check that the blower can move enough air through your existing ductwork, because a furnace that fits the load on paper still struggles when the returns are undersized. An oversized furnace short-cycles, runs louder and leaves bigger temperature swings, so the right new furnace is sometimes smaller than the old one.
80% or 96–98% AFUE: which furnace?
AFUE is the share of the fuel that ends up as heat in the house. An 80% furnace sends the rest up a metal flue. A 96–98% condensing furnace pulls so much heat out of the exhaust that water condenses inside it, so it vents through PVC and needs a drain.
| What differs | 80% AFUE | 96–98% AFUE (condensing) |
|---|---|---|
| Fuel turned into heat | About 80 cents of each fuel dollar | About 96 to 98 cents |
| Gas burned for the same heat | Baseline | About a sixth less, on paper |
| Venting | Metal flue into a chimney or metal vent | PVC exhaust out a wall or roof, plus a PVC intake on direct-vent models |
| Condensate | None | Needs a floor drain or a condensate pump |
| Water heater | Can keep sharing the chimney | May be left alone in the chimney and need a liner |
| Our installed price | Roughly $4,500–$6,000 | Roughly $6,500–$9,500 |
With a Minnesota heating season this long, the condensing furnace is the usual pick for a house you plan to stay in. The 80% furnace still has a place: when a sidewall or roof vent is hard to route, when you're selling soon, or in a space that barely runs. Going from 96% to 98% is a much smaller step than going from 80% to 96%, and our post on 96% vs 98% AFUE covers when those last two points are worth paying for.
Single-stage, two-stage or modulating: which is worth it?
| What differs | Single-stage | Two-stage | Modulating |
|---|---|---|---|
| How it fires | Full fire every time it runs | Low fire most of the time, high fire on the coldest days | Adjusts its firing rate in small steps to match the load |
| Cycles | Shorter and more frequent | Longer and quieter | Longest and steadiest |
| Temperature swings | Most noticeable | Smaller | Smallest |
| Price within each AFUE band | Lower | Middle | Higher |
In practice, a Minnesota house needs full capacity only on the coldest nights of the year. The rest of the season, a two-stage or modulating furnace runs longer, quieter cycles at low fire, which evens out the temperature between floors. Pair it with a variable-speed blower and you also get steadier airflow for the AC in summer. Single-stage still makes sense on a tight budget or in a small, simple house.
What a Minnesota install has to get right
Terminations above the snow line
Going from an 80% furnace to a condensing one means new venting. The PVC pipes usually run out through the rim joist, and the terminations have to clear the expected snow line and keep required distances from windows, doors and the gas meter. A termination tucked into a corner where snow drifts will shut the furnace down in the first big storm, so placement matters more here than the drawings in the installation manual suggest.
A drain that can't freeze
The condensate needs somewhere to go: a floor drain, or a condensate pump if there isn't one close by. We keep the drain line out of cold garages and crawlspaces, where it can freeze and shut the furnace down.
The orphaned water heater
If the water heater shared the chimney with the old furnace, it's now alone in a flue sized for two. That flue can run cold enough for condensation to form inside the chimney and weaken the draft. The usual fixes are a correctly sized chimney liner or a power-vent water heater, and the quote lists whichever one your house needs. It comes up often in older houses with masonry chimneys, which Minneapolis and Saint Paul have plenty of. Our local pages cover furnace replacement in Minneapolis and Saint Paul.
Older ductwork and propane
In 1910s–1940s city houses, forced air often replaced a gravity furnace, and the return ducts are frequently too small for a modern blower. A new furnace can't fix that alone, so we check the returns before we quote. Past the gas lines, the new furnace has to be set up for propane, with orifices and gas valve settings matched to the fuel.
Dry winter air
A furnace replacement is a good time to add a whole-home humidifier, since it mounts on the furnace. In cold weather most houses do well around 25–35% relative humidity, lower in deep cold, which keeps windows from fogging and frosting.
How does a furnace install work?
- Walkthrough and load calculation. We look at the furnace, ductwork, venting route, drain and gas line, and run a Manual J on the house.
- Written quote. You get a flat-rate price that lists the furnace, venting, condensate, any liner or coil work, the permit and haul-away.
- Permit. We pull the mechanical permit before work starts.
- Install day. We shut off gas and power, remove the old furnace and set the new one, then connect the ductwork, gas, electrical, venting and condensate line. Most straightforward replacements are done in one day; a venting conversion or chimney liner can add time.
- Startup. The technician checks gas pressure, temperature rise and combustion, sets the blower speeds and tests the safety switches.
- Walkthrough. We show you the filter, the thermostat and where the condensate drains, and leave the warranty paperwork with you.
- Inspection. A city inspector checks the gas piping, venting and clearances. Our permit guide explains how that works in Minneapolis and Saint Paul.
Installs carry a 2-year labor warranty on top of the manufacturer's parts warranty. Many manufacturers require online registration within a set window, often 60 days, for their longer parts coverage, so register the furnace promptly and keep the paperwork.
How much does a new furnace cost?
Installed furnaces run $4,500–$9,500 with us: roughly $4,500–$6,000 for an 80% AFUE furnace and $6,500–$9,500 for a 96–98% AFUE condensing furnace. Within those ranges, the price moves with:
- Two-stage or modulating burners and a variable-speed blower
- Converting from chimney venting to PVC, plus any chimney liner for the water heater
- A condensate pump when there's no floor drain nearby
- A coil transition, or a new coil if the AC is due too
- Propane setup on homes past the gas lines
The quote is written and flat-rate, pricing is the same in every town we serve, and financing is available. Our furnace replacement cost guide walks through each line item, and the Minneapolis HVAC cost page and pricing page put these numbers next to our other prices. If you're comparing brands, start with the best furnace brands for Minnesota and Carrier vs Trane vs Lennox. For a heat pump paired with a gas furnace, see heat pumps and dual fuel. And if you're not sure the old furnace is done, a repair visit answers that first: it's a $79 trip charge, waived if you approve a repair instead.
Utility rebates in 2026
We help with utility rebate paperwork where the program allows it. Programs and amounts change every year, so check the current terms with your utility before you buy:
- CenterPoint Energy supplies gas in Minneapolis and much of the metro. Its heating rebates let you use the heating dealer of your choice. The furnace has to be AHRI- or ENERGY STAR-listed with a verified AFUE, the application goes in during the same calendar year as the install, and an estimate doesn't count as proof of purchase.
- Xcel Energy supplies gas in Saint Paul. Its furnace rebate page points to participating contractors, so ask Xcel whether your rebate needs one.
- Other utilities run their own programs, including Minnesota Energy Resources and the municipal utilities, and Focus on Energy is the statewide program on the Wisconsin side.
The federal 25C tax credit ended for furnaces placed in service after December 31, 2025, so don't count on it. Our 2026 rebate guide covers the Xcel Energy and CenterPoint programs in more detail.
What's included with furnace installation?
- Manual J load calculation to set the furnace size
- Written, flat-rate quote listing equipment, venting and extras
- Mechanical permit and city inspection
- Venting and condensate work: PVC, chimney liner or drain as needed
- Removal and haul-away of the old furnace
- Startup checks and a walkthrough of the new furnace and thermostat
- 2-year labor warranty, plus rebate paperwork help where the program allows it
Furnace Installation questions
Is a 96% furnace worth it over an 80% furnace?
In most Minnesota homes that heat with natural gas or propane, yes. A 96% furnace turns 96 cents of every fuel dollar into heat, against 80 cents for an 80% furnace, and our heating season is long. An 80% furnace still makes sense when a sidewall vent is impractical, when you're selling soon, or when the furnace heats a space that barely runs. We price both when both fit.
What size furnace do I need?
The size comes from a Manual J load calculation: square footage, insulation, windows, air leakage and orientation, figured against our winter design temperature. Plenty of older furnaces were oversized, and sizing a replacement from the old nameplate repeats the mistake. An oversized furnace short-cycles, runs louder and leaves temperature swings, so the right new furnace is sometimes smaller than the old one.
How long does a furnace installation take?
Most straightforward replacements are done in one day. The old furnace comes out, the new one is set, and the gas, electrical, ductwork, venting and condensate are connected before a startup check of gas pressure, temperature rise and combustion. Converting from chimney venting to PVC, adding a chimney liner or working in a tight mechanical room can add time. The city inspection is scheduled separately.
Do I need a permit to replace a furnace?
Yes. Replacing a furnace normally requires a mechanical permit from the city, or from the county or state where the city has no building department. We pull the permit, and an inspector checks the gas piping, venting and clearances. Unpermitted work can cause problems when you sell the house or file an insurance claim.
What happens to my water heater if the furnace switches to PVC venting?
If the water heater shared a masonry chimney with the old 80% furnace, it now vents alone into a flue sized for two appliances. That flue can run too cool, and the condensation damages the chimney and can hurt the draft. The fix is usually a properly sized chimney liner or a power-vent water heater. We check this on every conversion and put the cost in the quote.
Which furnace brand is best for Minnesota?
The one that's sized and installed right. Most major brands sell both 80% and high-efficiency condensing furnaces, with single-stage, two-stage and modulating options, and sizing, venting and startup setup decide more about how a furnace runs than the name on the cabinet. Compare the warranty terms and the features you're paying for, like staging and a variable-speed blower. We service every major brand, so later repairs aren't tied to one company.
Will a new furnace work with my existing air conditioner?
Usually, but check the AC's age and refrigerant. The indoor coil sits on top of the furnace, so a new furnace may need a transition piece or a different coil. If your AC still runs on R-22, which hasn't been produced or imported since 2020, it can make sense to replace both together and avoid paying for coil work twice.
Has the federal tax credit for furnaces ended?
Yes. The federal 25C tax credit ended for furnaces placed in service after December 31, 2025. Utility rebates from Xcel Energy, CenterPoint Energy and others are separate programs that change each year, so check with your utility for current offers. CenterPoint Energy's furnace rebates let you use the dealer of your choice, while some other programs require a registered contractor, so ask before you buy.
Sources
- heating rebates centerpointenergy.com
- ENERGY STAR energystar.gov
- AHRI Directory of Certified Product Performance ahridirectory.org