Furnace Replacement Cost in Hermann: What Changes the Price

What do published figures say about furnace cost?

Regional figures, not our prices. No source publishes furnace prices for Hermann or Gasconade County, so the table marks each number as regional or national. Treat all of them as planning figures dated 2026, and none as a quote from us.

The gap between $3,200 and $6,200 is the point of this article. Two neighbors can get quotes that far apart and both be fair, because the houses differ. Propane and electric furnaces are not broken out in these sources, so we will not guess at a number for them here.

Furnace replacement cost: seven things that change the price

These run roughly from biggest to smallest effect, though any one of them can lead on a particular house.

Efficiency and venting

The federal minimum for a gas furnace is 80% AFUE. An 80% furnace vents hot exhaust up a metal flue or chimney. A condensing furnace in the 90s pulls out so much heat that exhaust leaves through plastic pipe, and it needs a drain for the condensate. That means a new vent route and a drain, and in an older house either one can be simple or awkward.

What else shares the chimney

Take a furnace off a shared chimney and the gas water heater left behind may no longer draft correctly, because a flue sized for two appliances is now serving one. It can need a liner or a new vent. Ask about this before you sign, because it is a safety item and a real line on a quote.

Fuel at the house

Inside Hermann city limits, gas comes from the municipal system. Outside town, a home might be on Spire, on propane or on electric heat, so read your bill or tank. Going from propane to natural gas, or fitting a furnace for propane, changes parts and setup. Switching fuels entirely adds lines for gas piping or tank work, and those belong in the quote.

Sizing

Do not let anyone copy the size off the old furnace. Older homes were often oversized from the start, and insulation or window changes have altered the load since then. An ACCA Manual J load calculation sets the real number. An oversized furnace short cycles, which wears parts and leaves rooms uneven, while the right size can sometimes cost less to buy.

Ductwork condition

A new furnace pushes air through the ducts you have. Hermann's median home dates to 1956, and 30.7% of homes date to 1939 or earlier (Point2Homes), so plenty of duct systems have outlived several furnaces. Undersized returns choke a new blower. The St. Louis add-on of $1,500 to $4,000 reflects this and a smaller sealing job is a different scope. Our duct repair page explains what a test turns up.

Access and old-house details

A clear basement with a straight stairway is the easy case. A low crawl space, a narrow cellar door or a tight attic adds labor. Riverside homes in New Haven, about 22 minutes and 16 miles from our office, can bring stone foundations and tight stairs, and historic properties anywhere can limit where a vent exits. Ask your city whether exterior changes need review.

Permits and code items

Most Missouri jurisdictions require a mechanical permit even on a like-for-like swap, according to the Missouri HVAC Authority. Rules here are local, and the St. Louis fee above does not tell you what your town charges. Ask city hall or the county, and ask every contractor who pulls the permit. Updates to gas piping, combustion air or drains can also appear as code items.

Three Hermann-area houses, worked through

These add up only the published figures above, so they show how a total grows. They are not quotes.

A 1950s ranch with a clear basement. The furnace sits near the stairs, the ducts test fine and the chimney serves nothing else. That house can stay close to the $3,200 to $6,200 regional range, plus a permit at $75 to $200 if your town charges one on that scale.

A pre-1940 brick home with old returns. Add the $1,500 to $4,000 ductwork figure and the same furnace now totals about $4,775 to $10,400. The spread is wide because the duct work may be a small return or a real rebuild, and only a visit tells you which.

A 1980s home with an aging AC. Replacing both is priced at $7,200 to $12,800 for a 3-ton pairing. Doing both at once settles the coil match and spares you a second install day, so it is worth pricing even if the AC still runs.

Does a higher AFUE pay for itself?

Run the numbers on your own bill. Moving from 80% to 96% AFUE burns about 16.7% less fuel for the same heat, because 80 divided by 96 is 0.833.

Here is an example with a round figure. If your home spends $1,000 a year on gas for heat, that saves about $167 a year. If the condensing option costs $1,500 more once the vent and drain are counted, it takes about nine years to pay back. A propane home on a higher fuel bill gets there sooner, and a well-insulated house with a small bill may never get there. Ask for both options priced in full, then divide.

How to compare two furnace quotes

Line up the same things side by side, or the totals mean nothing.

• Model number and AFUE of the furnace
• Whether a Manual J was done, and the resulting size
• Venting, drain and any chimney or water heater work
• Duct changes, thermostat and any gas piping
• Permit, and who pulls it
• Haul-away of the old furnace
• Written warranty terms from the manufacturer and the installer

A quote that is much lower often leaves out a line that shows up later, so ask what is excluded.

What we tell customers before they replace a furnace

Price a replacement before you need one. Once a furnace passes about 15 years, take a photo of the data plate and ask us for a clear, upfront quote during a mild month. Knowing the number ahead of time beats shopping with a cold house and a repair estimate in hand. Our furnace replacement page lays out the options, and furnace installation covers a new system where none exists.

Check whether money is available too. Spire's form for its October 2025 program year listed $200 to $300 for qualifying gas furnaces, for Spire customers only, and that may have changed. Our Missouri rebates guide shows what to verify. When you are ready, call (209) 563-1270 and our office will set up a look at the house.