Furnace Replacement Cost in St. Louis: What Changes the Price

Furnace replacement cost in St. Louis most often falls between $3,000 and $8,000 for a standalone swap, according to Budget Heating's 2026 buying guide. These are market ranges from third-party sources, not a Kenan Corporation quote. The final number turns on six things, and four of them are decisions you make.

What is the furnace replacement cost in St. Louis?

Budget Heating's 2026 guide says most homeowners spend $4,000 to $10,000 installed, including unit, materials, labor and permits. HVAC Project Cost, in a July 17, 2026 update that cites contractor data from Kansas City and St. Louis, lists $4,200 to $9,500 for a gas furnace across Missouri. Angi's 2026 figure for a full HVAC replacement in St. Louis is $4,755 to $11,888, averaging $7,133, with labor at $75 to $150 per hour.

Equipment is only part of it. Budget Heating prices the furnace alone by tier:

What changes the price of a new furnace?

Six items move the quote, and a good written estimate lists each one:

• Efficiency tier. Federal law sets an 80 AFUE floor for new gas furnaces. Anything above it costs more.
• Stages and blower. Single-stage is cheapest. Two-stage and modulating units run quieter and hold steadier temperatures.
• Size. It should come from a load calculation of the house, not from the old furnace's label.
• Venting. High-efficiency furnaces vent through plastic pipe and need a condensate drain, which adds labor, per Budget Heating.
• Ductwork. HVAC Project Cost says duct sealing or partial replacement can add $1,000 to $3,500, and tight wall chases in pre-1970 brick homes can add $500 to $1,500 in labor.
• Permit and disposal. Budget Heating puts permits and labor together at about $800 to $2,125.

Older brick houses add a venting wrinkle. Many have a masonry chimney that the furnace and water heater share. When a condensing furnace replaces the old one, the water heater is left alone in that chimney, and the flue may need a liner or a new vent path. Ask the installer how they will handle it, and make sure the answer appears as a line on the quote rather than as a surprise on install day.

Is a high-efficiency furnace worth the extra cost?

It depends on how long you will own the house and how the ducts look. ENERGY STAR says certified northern-region gas furnaces can save about $160 a year over baseline models. Budget Heating's tiers put the equipment premium for a 96% two-stage unit over an 80% unit at roughly $600 to $1,300. At $160 a year, that takes about four to eight years to recover, before any venting work.

A 96% furnace attached to leaking ducts wastes much of what you paid for. Sealing and sizing deserve the same attention as the AFUE number. Our furnace replacement page explains how we compare options, and furnace installation covers the install steps.

Why is a bigger furnace not a better one?

Size is the one factor where paying more can make things worse. A furnace sized from the old nameplate inherits every mistake of the 1980s install, and many older St. Louis houses have since gained attic insulation, storm windows or sealed ducts. A load calculation often shows the house now needs less heat than the old unit makes. An oversized furnace heats the air fast, shuts off, then restarts again and again, which wears parts and leaves rooms uneven.

The trade-off runs the other way too. A furnace sized tightly to the calculation has less reserve on the coldest night, and a leaky house can feel it. Ask the installer to show the numbers, the design temperature used and whether a two-stage unit covers both mild days and extremes. Two-stage and modulating units earn part of their premium by handling that spread.

What if the AC is also old?

If both the furnace and the air conditioner are near 15 years, price them together. One visit, one permit and one set of ductwork decisions can cost less than two separate jobs, though that saving depends on the quote, not a rule. It also opens a third option: a heat pump paired with a gas furnace, called dual-fuel. Ameren Missouri's 2026 rebate chart lists $2,000 per system for air-source heat pumps at 15.2 SEER2 or higher in dual-fuel cases. The chart is valid only through December 31, 2026, so a 2027 chart may differ. The work must go through an Ameren participating contractor, and we do not claim that status. Confirm any rebate in writing before you sign, and read our heat pump versus furnace guide for the fit question.

What should a written furnace quote include?

A quote you can compare names the model, the AFUE, the size in Btu, what is removed, the venting and condensate work, any duct changes, the permit and who pulls it. In the City of St. Louis, Ordinance 70800 requires replacement units to be installed by a mechanical contractor licensed in the City, and the work needs a permit with a $25 application fee. St. Louis County requires a permit to replace heating systems as well. For Shrewsbury, confirm the rule with the local building office.

Ask any contractor, including us, for the license number that applies in your jurisdiction. Missouri has no statewide HVAC license, so cities and counties set the rules.

How do you compare three quotes line by line?

Totals hide the differences. Lay the quotes next to each other and check each row below.

A deadline that expires tonight is a pressure tactic, not a cost factor. Kenan Bruce Martz founded this company in 2010 because he disliked hard-sell pitches in the trade, and a quote that cannot survive a night's sleep deserves a second look.

The federal 25C credit is over. The IRS says it is not allowed for property placed in service after December 31, 2025. Our rebates guide lists what is left to check.

From the field: replacement is not always the answer

A Google reviewer, Wendy R., wrote that another company called for a new furnace because the heat would not come on. That company had not checked any parts. Kenan found a capacitor causing the problem and fixed it, so no furnace purchase was needed.

Another reviewer, Candice F., called Kenan "Great at explaining things and giving you options." That is the standard to hold any quote to. Our approach is simple: we would rather repair your system than pressure you into a new one, and when a furnace is truly at the end of its 15 to 20 years, we say so and show the options. If you are still deciding, read the furnace repair page first.

Get a furnace price in writing

Call (321) 478-0693 to describe the furnace, its age and the symptom. We are open 24 hours, and we run a load calculation before sizing a replacement. You get a clear, upfront quote before any work starts, with each item above on its own line.