Is a higher-AFUE furnace always the better buy?

Not automatically. Higher efficiency saves gas every month, but the payoff depends on how long you'll stay in the home, your gas usage, and whether your venting setup supports a condensing furnace without extra work. We walk through that math with you before recommending one.

Do I have to replace my AC when I replace my furnace?

No, but it's worth evaluating. The furnace blower moves air for the AC too, and if the AC is near the end of its life, doing both at once often costs less than two separate installs. If your AC is newer, we'll match the furnace to it.

How long does a furnace installation take?

A straightforward swap is usually done in a day. Jobs that involve ductwork changes, new venting, or converting to a different furnace type can take longer. We'll tell you the timeline in the quote.

Can I finance a new furnace?

Yes. We offer financing options with approved credit so a mid-winter replacement doesn't have to come out of pocket all at once. Details are on our financing page or over the phone.

What size furnace does my house need?

It depends on square footage, insulation, windows, and layout — not just matching whatever's there now. A proper load calculation tells us the right BTU rating. Oversized furnaces short-cycle and heat unevenly, so bigger is not better.

heating

What Does a New Furnace Cost in the St. Louis Area?

February 3, 2026

There’s no honest single number for what a new furnace costs in St. Louis, because the price depends on the furnace you pick and the house it’s going into. The big variables: the size (BTU rating) your home needs, the efficiency level (AFUE), whether it’s a single-stage, two-stage, or modulating unit, the brand tier, and how much work the installation itself involves. Anyone who quotes you a firm price without seeing your home is guessing. What we can do is explain exactly what moves the number, so when you get quotes — from us or anyone else — you can read them intelligently.

Why Does Furnace Size Matter So Much?

Furnaces are rated in BTUs, and your home needs a specific amount of heating capacity based on its square footage, insulation, window quality, ceiling height, and layout. A proper contractor runs a load calculation instead of just matching the old unit’s size — because the old unit may have been sized wrong from day one, or your home may have changed since it was installed (new windows, added insulation, a finished basement).

Bigger costs more, but oversizing is a mistake, not an upgrade. An oversized furnace blasts heat, satisfies the thermostat fast, and shuts off — then repeats. That short-cycling wears parts, heats rooms unevenly, and wastes fuel. Right-sized is the goal.

What Is AFUE and How Does It Change the Price?

AFUE (Annual Fuel Utilization Efficiency) is the percentage of your gas that becomes heat in your home instead of going up the flue. An 80% AFUE furnace sends about a fifth of your fuel out the vent. High-efficiency condensing furnaces run in the 90s, pulling extra heat out of the exhaust before it leaves.

Higher AFUE means a higher equipment price and, often, added install work — condensing furnaces vent through PVC pipe (usually out a side wall) and need a drain for the condensate they produce. In exchange, you burn less gas every month for the life of the unit. Whether that trade pays off depends on your gas usage, how long you plan to stay, and what your existing venting looks like. Missouri winters give high-efficiency units plenty of runtime to earn their keep, but it’s a case-by-case call, and we’ll give you our honest read for your house.

Single-Stage, Two-Stage, or Modulating — What’s the Difference?

This is about how the furnace delivers heat, and it’s a real comfort difference, not just marketing.

A single-stage furnace has one setting: full blast or off. It’s the simplest and least expensive, and it heats your home fine — just with bigger temperature swings.

A two-stage furnace can run at a lower output most of the time and step up to full power on the coldest days. Longer, gentler cycles mean steadier temperatures, quieter operation, and better air mixing between floors.

A modulating furnace adjusts its output in small increments, holding the temperature almost dead-flat. It’s the top of the comfort ladder and the top of the price ladder.

If your home has hot-and-cold-spot problems or a floor that never feels right, staging is worth a conversation. If you just want reliable heat at the lowest entry price, single-stage still does the job.

What Installation Factors Move the Quote?

Two identical furnaces can carry very different installed prices depending on the house. Things that add labor and materials:

Venting changes. Moving from an 80% furnace to a condensing model means new PVC venting, and sometimes the old metal flue needs relining for the water heater it left behind.
Ductwork condition. Crushed, undersized, or leaky ducts choke a new furnace. Sometimes a plenum needs rebuilding or a return needs to be added for the system to breathe right.
Location and access. A furnace in a tight closet or a low crawl space takes more time than one in an open basement.
Electrical and gas line work. Older homes sometimes need updates to meet current code.
Extras. A new thermostat, media filter cabinet, or whole-home humidifier added at install time changes the total.

A good quote spells these items out. A vague one hides them until installation day.

How Should You Compare Furnace Quotes?

Compare quotes line by line, not bottom line by bottom line. Check that each quote covers the same equipment class — same AFUE range, same staging, comparable brand tier. Confirm what’s included: permit, haul-away of the old unit, new thermostat, venting work, warranty registration. Ask about both the parts warranty (from the manufacturer) and the labor warranty (from the contractor) — those are separate things, and the labor warranty tells you how much the installer trusts their own work.

Be cautious with any bid dramatically lower than the rest. Furnace equipment costs contractors roughly the same; a rock-bottom price usually means corners cut on install quality, and installation quality is what determines whether that furnace hits its rated efficiency and lifespan. You can see the equipment lines we carry on our furnaces page.

What If the Timing Is Bad Financially?

Furnaces have a habit of dying during the first hard cold snap, not when it’s convenient. That’s why we offer financing with approved credit — it spreads the cost into monthly payments instead of one lump sum in December. It’s also worth checking our current promotions before you buy, and asking about utility rebates for high-efficiency equipment, which come and go throughout the year.

The only way to get a real number for your home is an in-person evaluation, and ours come with an upfront, no-surprises quote. Learn more about how we handle furnace installation, or call (636) 887-2800 and we’ll set up a visit.