High-Efficiency Furnace Cost in St. Louis: 2026 Price Guide
Most St. Louis homeowners should expect a high-efficiency gas furnace (96% AFUE or higher) to cost roughly $6,000 to $10,000 or more installed. That figure comes from Angi’s St. Louis pricing data. Your own number depends on your home’s size, your ductwork, the venting, and whether you choose a single-stage, two-stage or modulating unit. Below we explain what is inside that range, why two quotes for the “same” furnace can differ by thousands, and how to compare bids so you pay for real efficiency and not just a label.
TL;DR
- Installed high-efficiency furnaces in St. Louis typically run about $6,000 to $10,000+. Mid-efficiency units (90 to 95% AFUE) run about $4,000 to $7,500, and standard 80% units about $2,500 to $4,500, per Angi.
- The unit is only part of the bill. Venting, ductwork changes, permits and removing the old furnace often account for the gap between the equipment price and your final invoice.
- Ask for itemized, apples-to-apples quotes, and make sure the contractor sizes the system with a Manual J load calculation.
- Replacing in spring or fall, before an emergency, is the most reliable way to avoid paying a rush premium.
- Federal efficiency rules are tightening, and tax credit rules have changed, so confirm any incentive before you count on it.
Table of Contents
- What a high-efficiency furnace costs in St. Louis
- Why the installed price is more than the furnace
- What moves your price up or down
- Is the high-efficiency upgrade worth the extra money?
- Rules and incentives: what to know before you buy
- How to compare furnace quotes
- Our perspective: what we’d tell a neighbor
- Planning a furnace replacement in St. Louis or Jefferson County?
- FAQ
- Sources
What a high-efficiency furnace costs in St. Louis
“High efficiency” means a condensing gas furnace with an AFUE rating (annual fuel utilization efficiency) of roughly 95 to 98%. An AFUE of 96% means that about 96 cents of every dollar of gas you buy becomes heat in your home. An older 80% furnace sends the other 20 cents up the flue.
Here are the installed ranges for the St. Louis area. Installed means equipment, labor and standard accessories:
| Efficiency tier | AFUE | Typical installed cost, St. Louis |
|---|---|---|
| Standard | 80 to 89% | $2,500 to $4,500 |
| Mid-efficiency | 90 to 95% | $4,000 to $7,500 |
| High-efficiency | 96%+ | $6,000 to $10,000+ |
Source: Angi, How Much Does a New Furnace Cost in St. Louis.
Other published estimates run lower for the metro as a whole. One local cost database puts all furnace replacements in St. Louis at $2,446 to $7,339, which blends in many basic 80% swaps. Treat any range as a starting point. A website cannot see your basement, your flue or your ducts, and we don’t publish a flat price for the same reason.
The same Angi page says the average St. Louis home needs a furnace in the 56,000 to 72,000 BTU range. If a quote lands far outside that for a typical house, ask why.
Why the installed price is more than the furnace
Homeowners are often surprised that the equipment price on a spec sheet is a fraction of the invoice. One industry guide notes that the installed price can be two to three times the unit cost, because of the work around the furnace. In our experience in St. Louis and Jefferson County homes, these are the line items that matter:
- New PVC venting. A condensing furnace pulls so much heat out of the exhaust that the exhaust is cool and wet. It vents through plastic pipe, not the old metal flue, and it drains condensate. If your old furnace shared a chimney with a water heater, the water heater’s venting may need attention too.
- Ductwork adjustments. Older St. Louis homes often have undersized returns or leaky trunk lines. A high-efficiency furnace on poor ducts will not deliver what the spec sheet promises.
- Permits and inspection. Our own breakdown of furnace replacement costs in St. Louis covers permit fees that typically run $200 to $400. Fees vary by municipality, so ask who pulls the permit.
- Removal and disposal of the old unit.
- Gas line, electrical and condensate work, such as a new drain or a condensate pump if there is no floor drain nearby.
- Add-ons, such as a smart thermostat or air filtration, if you choose them.
A suspiciously low quote usually means some of these are missing. That doesn’t help you. It just moves the cost to a change order or to your gas bill.
What moves your price up or down
Single-stage, two-stage or modulating
A single-stage furnace is either on at full blast or off. A two-stage furnace has a low setting for mild days and a high setting for cold ones. A modulating unit adjusts in small steps. ENERGY STAR guidance points buyers toward at least two capacity stages or modulation, because they keep the temperature steadier and help with humidity. They also reduce short-cycling, where a furnace turns on and off too often and wears out parts early.
In practice, this is where much of the price spread inside the high-efficiency tier comes from. A single-stage 96% unit sits at the low end of the range. A variable-speed, modulating unit is at the top.
Home size and heat loss
Bigger isn’t better. An oversized furnace short-cycles, costs more up front and runs less comfortably. The right size comes from a Manual J load calculation, which accounts for your square footage, insulation, windows and air leakage. It is not a rule of thumb or a copy of whatever was there before. ENERGY STAR’s materials list correct sizing and duct checks as part of quality installation. Without them, a pricey new system can perform like a basic one.
Access and house type
South City brick two-families, 1960s ranches in Crestwood and Affton, and newer Jefferson County builds in Arnold and Fenton all have different venting paths, basement layouts and attic or crawlspace access. Tight access means more labor hours. A vent run that has to travel 40 feet costs more than one that goes straight out a rim joist.
Timing
Cost data for the metro suggests that replacing in spring or fall can earn 10 to 20% discounts, while emergency same-day replacements carry a premium for overtime and urgency. We can’t promise a specific discount, but the principle holds: contractors have more flexibility in April and October than in a January cold snap.
Is the high-efficiency upgrade worth the extra money?
The extra upfront cost of a 96% furnace over an 80% one is real, often $2,000 or more by the ranges above. What you get back is lower gas use every month the furnace runs. Local contractors consistently describe the pattern: a high-efficiency furnace costs more upfront but less to operate.
How fast it pays back depends on your house:
- Older, drafty home with a big gas bill: the upgrade pays back faster, but only if the ducts and insulation aren’t wasting the savings.
- Well-sealed home with low usage: payback stretches out. Comfort features such as two-stage heat may be the better reason to choose the upgrade.
- You plan to stay 10+ years: the math improves every year.
- You plan to sell soon: a working, newer furnace helps, but you may not recoup the premium.
A race car engine on flat tires goes nowhere fast. One industry guide uses exactly that comparison for a high-efficiency furnace on old, leaky ductwork. If your ducts leak, fix that first, or in the same project.
Rules and incentives: what to know before you buy
Federal efficiency standards are rising
The Department of Energy has finalized a rule requiring residential gas furnaces to reach at least 95% AFUE, effective late 2028. The DOE projects household utility savings of about $1.5 billion a year nationwide. In plain terms, today’s high-efficiency furnace is where the market is headed. If you want a broader view of how efficiency rules affect homeowners, this homebuyer guide on efficiency features and regulations is written with California in mind, but the thinking carries over.
The federal tax credit: verify before you count on it
IRS guidance on the Energy Efficient Home Improvement Credit (Section 25C) described a credit of 30% of cost, up to $600 per item for a furnace, and said gas furnaces had to meet the top CEE tier, typically 97% AFUE in northern states. ENERGY STAR lists 97% AFUE or greater for North-region gas furnaces, which is a stricter bar than a 95% “high efficiency” label.
IMPORTANT: that guidance was written for 2025 and earlier. Credit rules change, and we don’t want you to budget around an incentive that may no longer apply to a furnace installed now. Before you sign, ask a tax professional whether any credit covers your installation date, and read the IRS home energy credits page for the current status.
Utility rebates
Gas and electric utilities in Missouri have offered rebates on high-efficiency equipment. Programs, amounts and deadlines change often, and typically require a licensed contractor and an active account with the utility. Check with your gas utility before the install, not after, and keep your invoice with the full model number.
How to compare furnace quotes
Here is the process we recommend to St. Louis County and Jefferson County homeowners:
- Get two or three written, itemized quotes. Each should list the model number, AFUE, stages, venting, permit, disposal and warranty terms.
- Ask for the load calculation. If nobody measured your house, the size is a guess.
- Ask about the ducts. A good contractor looks at them, tests them or at least tells you what they saw.
- Ask who pulls the permit and who schedules the inspection.
- Compare the same tier. A 96% two-stage bid next to an 80% single-stage bid isn’t a comparison.
- Be wary of pressure. A quote that’s good today only, with no time to think, deserves a second look.
- Read the warranty for both parts and labor, and see what registration it requires.
If you’re still deciding whether to replace or repair, our guide to three rules for deciding when to replace your furnace walks through age, repair cost and efficiency.
Our perspective: what we’d tell a neighbor
We’ve worked on heating systems in St. Louis County and Jefferson County for 50 years, and the most expensive furnace decisions we see are rushed ones. A furnace dies on the coldest night of the year, and the homeowner takes the first quote. Most of that stress is avoidable.
Our advice is simple. If your furnace is 15 or more years old, has had a couple of repairs, or is getting loud, get a replacement quote in the fall, while you still have heat and options. Choose the efficiency tier that fits how long you’ll stay and how your house is built, not the one with the biggest sticker. And pay as much attention to the installation as to the box. Venting, sizing and ductwork decide whether the efficiency on paper shows up on your gas bill.
We give you an honest diagnosis and a clear recommendation, including when the right answer is a repair and not a replacement. We don’t do high-pressure upselling, and we’d rather you understand your options and call us back than sign on the spot.
— Alan Ricotta
Planning a furnace replacement in St. Louis or Jefferson County?
If you want a straight answer on what a high-efficiency furnace would cost in your home, our team can look at your system and give you a clear, written recommendation. See our furnace replacement services, learn about furnace installation, or contact us from our heating page. If your system is older and you’re not sure whether it’s worth a repair, a seasonal visit through our maintenance plans can also catch problems before they become emergencies.
FAQ
How much does a high-efficiency furnace cost to install in St. Louis?
Expect roughly $6,000 to $10,000 or more installed for a 96%+ AFUE gas furnace, based on Angi’s St. Louis figures. The top of the range reflects variable-speed or modulating equipment, complicated venting or ductwork changes. A written quote after an in-home visit is the only way to get your real number.
Is a 96% AFUE furnace worth it over an 80% one?
Often yes, if you plan to stay in the home for years and your ducts are in decent shape. The higher upfront price comes back as lower gas use. In a well-sealed home with low heating bills, the payback is slower, so the comfort benefits of two-stage heat may matter more.
Does a high-efficiency furnace need different venting?
Yes. Condensing furnaces vent through PVC and drain condensate, instead of using a metal flue. That work is one reason the installed price is well above the unit price.
When is the cheapest time to replace a furnace?
Spring and fall, before the peak of winter or summer. Cost data for the St. Louis metro suggests contractors may discount 10 to 20% in shoulder seasons, while emergency replacements carry a premium.
Can I get a tax credit for a new furnace?
IRS guidance covered a 30% credit capped at $600 for qualifying furnaces, generally 97% AFUE and ENERGY STAR certified, but the rules changed over time. Check the IRS home energy credits page and talk to a tax professional before assuming it applies to your installation date.
Sources
- Angi: How Much Does a New Furnace Cost in St. Louis, MO?
- Cost to Renovate: Furnace Replacement in St. Louis
- Accelerate Net Zero: Carrier High Efficiency Furnace Price Guide
- ENERGY STAR: Equipment Solutions webinar slides
- ENERGY STAR: Furnaces Key Product Criteria
- IRS: Energy Efficient Home Improvement Credit FAQ
- IRS: Home energy tax credits
- U.S. Department of Energy: Residential furnace efficiency standards