Furnace Replacement in Hermann, MO

Repair or replace an old furnace? Five signs that settle it

Replace when the safety case or the money case fails. Either of these usually comes first in a house with a furnace past 15 years.

1. A failed heat exchanger. The repair is large and the furnace is old. Compare it with a new unit before anything else.
2. Age plus a big repair. Furnaces are commonly quoted at 15 to 20 years with maintenance. Spending heavily on a board or blower motor near the end of that range rarely pays.
3. Repeat calls. Two or three repairs in a couple of seasons usually mean the next one is coming.
4. Uneven rooms and rising bills. Worn blowers and dirty heat exchangers lose ground slowly, so compare your fuel use year on year.
5. Parts that are hard to find. With an old furnace, one back-ordered part can cost you days in freeze season.

Every furnace we are asked to replace gets the same honest check: if a modest repair buys several good years, we will tell you so. Hermann's roughly 116 freezing nights a year mean a weak furnace is rarely a problem you can wait out.

Which replacement fits: 80% AFUE or a high efficiency furnace?

The choice is really about your vent and drain. Federal rules set an 80% AFUE minimum for gas furnaces today, and DOE's Building America guideline places high-efficiency models at 90% to 98%.

That 16% is arithmetic: 80 divided by 95. Check it against your own gas or propane bill before deciding. Two-stage and variable-speed blowers add comfort more than savings, so buy them for long, even winter heat rather than payback.

A federal rule finalized in 2023 would raise the gas furnace minimum to 95% AFUE from December 2028. ACHR News reports the rule is back in court review and that DOE has proposed a delay, so treat that date as unsettled in late 2026.

What your existing house decides for you

A replacement inherits the house, so inspect what stays before choosing what goes in.

• Return ducts. Ductwork in a 1956 home was built for a different furnace. Measure before sizing, because a bigger unit on small ducts just gets louder.
• Sizing. A new Manual J load calculation is worth doing if you have added insulation or windows since the old furnace went in. Old furnaces are often oversized, so the new one may be smaller.
• The chimney. Pull the furnace off a shared masonry chimney and the water heater is left on a flue built for two.
• A drain. No floor drain near the furnace means a condensate pump.
• Vent exits on historic walls. About 30.7% of Hermann homes date to 1939 or earlier. Whether exterior work is reviewed in the Historic District is unconfirmed, so ask the city before running PVC through old brick.
• The fuel. Municipal gas, a utility line or propane all use different settings, so confirm which one is on your bill.

Line items a furnace replacement quote should show

Your quote should spell out each of these items, so you can compare offers line by line.

• Removal and haul-away of the old furnace
• A new furnace matched to the load, ducts and fuel
• Plenum and duct transitions to fit the new cabinet
• Gas connection with shutoff and leak test
• Vent work, including the review of any shared flue
• Condensate drain, on a condensing unit
• Thermostat check, and blower setup to match any AC coil
• Start-up readings, and a walkthrough of the new filter

How the changeover works

Most straightforward swaps run in this order.

1. We inspect the furnace, ducts, vent and drain, and read the data plate.
2. We quote repair and replacement side by side, and you choose.
3. We confirm the permit question with your city or county.
4. We shut off gas and power, then disconnect and remove the old furnace.
5. We set the new furnace and fit the plenum, gas, vent and drain.
6. We fire it, leak test it and measure gas pressure and temperature rise.
7. We show you the filter and shutoffs and leave the paperwork.

What does furnace replacement cost around Hermann?

Angi's St. Louis estimate, checked November 2026, puts a new furnace at about $4,285 on average, with most homeowners paying $2,605 to $6,142 installed. Replacing the AC at the same time is listed at $3,900 to $14,880. These are regional figures, not our prices.

Five items move the number: furnace efficiency, vent changes, chimney relining, return duct work and access to the basement. For your own house, ask us for a clear, upfront quote. Do not build the budget around a rebate: Spire's rebates need an enrolled contractor before work begins, and Ameren's programs only apply to Ameren customers.

Why replace with Brian Grannemann Services?

• Weber S. says we have worked for him about a half dozen times and calls us "fair and responsive to your needs," which matters most when a quote could go either way.
• We have worked from Hermann since 1998, so you know where to find us after the old furnace is gone: 124 E 10th St.
• One reviewer, Donna M., praises the safety precautions, and a swap touches gas, venting and combustion all at once.
• Our trades include electrical and plumbing, which helps when a new unit needs a circuit or a drain.

Caring for the new furnace

Keep the filter on schedule, keep outdoor vent pipes clear, and book a yearly furnace maintenance visit so small problems stay small. Building new or adding a system instead? Furnace installation is the page for that.

We replace furnaces across our area, including New Haven, Rhineland, Owensville and Bland. Call (209) 563-1270, and have a photo of the data plate ready.