# What Does a New HVAC System Cost in St. Louis? ## HVAC Installation Cost If you've searched "how much does a new HVAC system cost," you've probably seen a range wide enough to be useless: somewhere between $3,000 and $15,000, depending on the article. That's not wrong, it's just not helpful. HVAC replacement cost in St. Louis depends on your home's size, your existing equipment, your ductwork condition, and which system type makes sense for you. A two-ton AC replacement in a 1,200-square-foot ranch is a fundamentally different project than replacing a furnace and AC together in a 2,800-square-foot two-story with aging ductwork. This guide gives you real price ranges by system type, explains what drives the variation, and tells you how to get an estimate that actually reflects your home, not a national average. ![ac install](https://www.aircomfortservice.com/wp-content/uploads/2026/06/IMG_7041-scaled.jpg "AC install")## Price Ranges by System Type These are installed cost ranges for residential HVAC replacement in the St. Louis metro. This includes equipment plus labor, permits, and standard refrigerant. ### [Central Air Conditioner (AC Only)](https://www.aircomfortservice.com/air-conditioning/air-conditioning-installation/) **$3,500-$8,000 installed** Replacing just the outdoor condenser and indoor coil and keeping your existing furnace and ductwork is the most common single-system replacement. The range reflects equipment tier (standard vs. high-efficiency) and home size. A standard efficiency (SEER2 14.3-16) unit for a mid-size home lands in the $3,500-$5,500 range. High-efficiency systems (SEER2 18+) for larger homes push toward $7,000-$8,000. ### [Gas Furnace](https://www.aircomfortservice.com/heating/furnace-installations/) **$2,800-$6,500 installed** Single-stage standard efficiency furnaces (80% AFUE) come in at the lower end. Two-stage or modulating variable-speed furnaces with 96-98% AFUE run higher, but the efficiency gains reduce monthly gas bills meaningfully over a 15-year lifespan. Most St. Louis homes doing a straight furnace replacement land between $3,500 and $5,500. ### Full System Replacement (Furnace + AC Together) **$6,500-$14,000 installed** Replacing both the furnace and air conditioner at the same time is almost always more cost-effective than replacing them separately. You save on labor, and matched-system efficiency ratings are higher than mismatched equipment. If one unit is aging and the other is within a few years of it, replacing both together is worth a serious look. ### [Heat Pump (Replaces Both Heating and Cooling)](https://www.aircomfortservice.com/air-conditioning/heat-pump-installation/) **$5,000-$12,000 installed** A heat pump handles both heating and cooling in a single system, making it a popular full-replacement option. Standard split-system heat pumps run $5,000-$8,000. Cold-climate heat pumps, which maintain efficiency in St. Louis winters better than older models run $8,000-$12,000 depending on size and tier. If your existing ductwork is in good condition, a heat pump replacement is worth pricing against a furnace + AC combo. ### [Boiler (Hydronic / Steam Heat)](https://www.aircomfortservice.com/heating-boiler-installation/) **$4,500-$12,000 installed** Boiler replacement cost depends heavily on system type. Standard hot water boiler replacements (existing system, no major piping changes) typically run $4,000-$8,000. High-efficiency condensing boilers push to $6,000-$12,000. Steam boiler replacements, common in older St. Louis neighborhoods, run $5,000-$10,000. If your home has existing radiators or baseboard heaters, replacing the boiler itself is usually far less disruptive than switching to a different system type. See our [boiler installation page](https://www.aircomfortservice.com/heating-boiler-installation/) for a full breakdown. ## What Drives the Price Variation You'll notice every range above spans several thousand dollars. Here's what moves the needle: **Home size and load calculation.** Equipment has to be sized correctly for your home. A system too small won't keep up in a St. Louis summer, and an oversized system short-cycles, wears faster, and delivers poor humidity control. Proper load calculation is the foundation of an accurate quote. Be cautious of any contractor who quotes without measuring. **Equipment efficiency tier.** The difference between an 80% AFUE furnace and a 97% AFUE furnace can be $1,200-$1,800 in equipment cost, but the higher-efficiency unit saves meaningfully on gas bills every year. The same logic applies to SEER2 ratings on AC and heat pump equipment. **Ductwork condition.** If your ductwork is leaking, undersized, or deteriorated, the new equipment will underperform until the distribution system is addressed. Duct sealing or partial replacement adds cost but protects the investment in new equipment. An honest contractor will tell you what they find. **Brand and product line.** Premium brands carry a premium for a reason, like tighter manufacturing tolerances, longer warranties, and better parts availability. But the installed cost difference between a mid-tier Carrier and a budget-brand unit often looks smaller over a 15-year horizon once you account for repair frequency. ## What Shouldn't Be In Your Quote A few things to flag if they appear in an estimate: **Oversized equipment.** Bigger is not better with HVAC. Contractors who quote a 4-ton system for a home that needs 2.5 tons are either cutting corners on the load calculation or padding equipment margin. Ask to see the load calculation. **Vague "system matching" charges.** If a contractor tells you that your existing coil or furnace "has to be replaced" without explaining why, ask them to show you. Sometimes it's true (mismatched efficiency ratings, incompatible refrigerant). Sometimes it's not. **Rushed timelines with no written quote.** A legitimate HVAC contractor provides a written, itemized estimate before any commitment. If the pressure is to sign before you have that, slow down. ## The Most Accurate Estimate Comes From Your Home National cost estimators and online calculators can give you a ballpark, but they can't account for your ductwork, your home's layout, your insulation, or your existing equipment. Two St. Louis homes of the same square footage can produce meaningfully different quotes based on how they're built. The most accurate way to price an HVAC replacement is a free in-home assessment with a technician who can evaluate your current system, measure your home's actual load, and explain your options in plain terms. Air Comfort Service offers free estimates on all new equipment installations. Use our [**Free Quote Tool**](https://www.aircomfortservice.com/get-a-free-quote/) to get the process started. Just answer a few questions about your home and current system, and we'll follow up with a no-pressure estimate. ## How to Compare Quotes If you're getting multiple bids, here's how to compare them fairly: - Make sure each quote specifies the same equipment tier (SEER2 rating, AFUE rating, brand and model number). A quote for a 14.3 SEER2 system is not comparable to a quote for an 18 SEER2 system. - Confirm permits are included. In St. Louis City and St. Louis County, HVAC replacement requires a permit. Any quote that doesn't include the permit is an incomplete quote. - Ask about both the manufacturer equipment warranty and any labor warranty the contractor offers. These vary significantly. - Look at the contractor's history, not just the price. A $500 lower bid from a contractor without local references or a track record is risky. Not sure what a new system will cost for your home? Use the **[Free Quote Tool](https://www.aircomfortservice.com/get-a-free-quote/).** Simply answer a few questions about your current setup and we'll follow up with a real, no-pressure estimate based on your home's specifics. Takes about two minutes. No commitment required. ## What Air Comfort Service Does Differently We've been replacing HVAC systems in St. Louis since 1969. Every estimate we provide is based on a real load calculation, not a square footage rule of thumb. We'll tell you what size system your home actually needs, what efficiency tier makes sense for your usage and budget, and whether your ductwork needs attention before new equipment goes in. We offer 0% APR financing for up to 72 months on new equipment installations (with approved credit). Explore our full range of [heating and cooling services](https://www.aircomfortservice.com/) or use the [**Free Quote Tool**](https://www.aircomfortservice.com/get-a-free-quote/) to get started. We're available 24/7. 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