Your furnace is limping into October, and you’re staring down a St. Louis winter wondering whether to replace it with another furnace or finally make the switch to a heat pump. The internet is full of conflicting advice, and most of it isn’t written for a climate that hits 24°F in January. We’ve been installing and servicing heating systems in the St. Louis area since 1964, and the honest answer is that the right choice depends on your specific home, not a generic national ranking.
What makes this decision harder right now is that both the equipment landscape and the incentive landscape shifted in the last couple of years. Modern heat pumps can do things older models couldn’t, and the rebate programs available to St. Louis homeowners in 2026 are different from what you’ll find in articles written even a year ago. Here’s what actually applies to your situation.
How Furnaces & Heat Pumps Actually Heat Your Home
A furnace generates heat directly, burning natural gas, propane, or oil inside a heat exchanger and pushing warmed air through your ductwork. Gas furnaces are rated by AFUE (Annual Fuel Utilization Efficiency), which measures what percentage of the fuel becomes usable heat. A 96% AFUE furnace converts 96 cents of every dollar of gas into heat and loses the rest in exhaust. Electric resistance furnaces are rated at 100% AFUE but are expensive to run because electricity costs more per unit of heat than gas.
A heat pump works differently. It uses electricity to move heat that already exists in outdoor air into your home rather than generating heat through combustion. In summer, it reverses the cycle and moves heat out, functioning as an air conditioner. Because there’s no combustion, there are no exhaust byproducts and no carbon monoxide risk from a cracked heat exchanger. One system handles both heating and cooling, which matters if your home currently has neither.
Will a Heat Pump Keep Up With a St. Louis Winter?
It’s a fair question. St. Louis averages a January low near 24°F and a high near 41°F, with cold snaps into the single digits most winters. For years, the standard advice was that heat pumps weren’t a good fit here because they struggled once temperatures dropped below 25 to 30°F.
That advice reflected older equipment. Modern cold-climate heat pumps, which use variable-speed compressor technology, are engineered to deliver strong heating capacity down to around 5°F and reduced but still meaningful output well below that. The 35°F cutoff threshold that still appears in articles you’ll find online doesn’t reflect what current equipment can do. SEER2 and HSPF2 are the efficiency ratings that now apply to equipment manufactured after January 2023, and higher HSPF2 numbers indicate better heating-season efficiency.
That said, even a modern cold-climate heat pump can be pushed harder than makes economic sense during the coldest days of a St. Louis winter. This is why many homeowners here opt for a dual-fuel system, pairing an air-source heat pump for the bulk of the heating season with a gas furnace that takes over only when temperatures drop below a set switchover point. You get the heat pump’s efficiency during the long shoulder seasons and early winter, and the furnace’s raw heating power for the short stretches of bitter cold.
Comparing Costs: Upfront, Monthly, & 2026 Incentives
Cost comparisons between these systems involve three separate numbers: what you pay to install it, what you pay to run it, and what programs exist to reduce either.
Upfront & Installation Costs
Gas furnace replacement in a home with existing ductwork and a working gas line is typically the lower-cost installation. A heat pump adds outdoor equipment and, in a dual-fuel configuration, works alongside the existing furnace rather than replacing it entirely, which affects how the total cost is framed. A full heat pump system providing both heating and cooling can cost more upfront than a furnace-only replacement, but if your home also needs an air conditioner, the comparison shifts because a heat pump serves both functions.
Monthly Operating Costs
Because heat pumps move heat rather than generate it, they produce more usable heat per unit of electricity than electric resistance heating. During mild and moderately cold weather, that efficiency advantage can mean meaningfully lower monthly bills compared to running a gas furnace, depending on local gas and electricity rates. When temperatures fall deep enough that the gas furnace in a dual-fuel setup takes over, that efficiency advantage pauses, but those days represent a small fraction of the total heating season in St. Louis.
What Incentives Actually Apply in 2026
Two things changed recently that most online articles don’t reflect. First, the federal Section 25C Energy Efficient Home Improvement Credit, which covered up to $2,000 for qualifying heat pumps, expired for equipment placed in service after December 31, 2025. That credit isn’t available for 2026 installations.
Second, Ameren Missouri replaced its prior standalone heating and cooling rebate program with the Pay As You Save program, known as PAYS. In 2026, Ameren Missouri’s PAYS program offers a $2,000 rebate for a qualifying ducted air-source heat pump at 15.2+ SEER2, but with an important condition: homes with existing gas heat must maintain the gas furnace as backup to qualify. That requirement means a dual-fuel configuration isn’t just a performance strategy for St. Louis winters; it’s specifically what Ameren Missouri’s 2026 rebate is designed to support. Any homeowner planning around these incentives should verify current program details directly with Ameren Missouri, since rebate structures can change mid-year.
Which System Fits Your Home?
Your starting situation changes the math more than any general ranking does.
- Existing Ductwork & a Working Gas Line
A dual-fuel configuration is worth a serious look. The heat pump handles the majority of the season, the furnace covers the coldest stretches, and the Ameren Missouri PAYS rebate is structured for exactly this scenario. You’re not abandoning your existing gas infrastructure. You’re adding a layer of efficiency on top of it. - Failed Furnace With No Air Conditioner
This is where a heat pump makes the strongest practical case. Rather than buying a furnace now and an air conditioner later, a single air-source heat pump or ductless mini-split handles both. The upfront cost is higher, but you’re replacing two future purchases, not one. - Lowest Possible Cost This Winter
A high-efficiency gas furnace is usually the fastest and lowest-cost path when a home already has ductwork and a gas line, and heating bills on natural gas tend to be predictable. Heat pumps deliver stronger long-term economics, but if the immediate constraint is budget, that matters. - Lower Long-Term Carbon Output
A heat pump running on grid electricity produces no direct combustion emissions at the home. As Missouri’s energy grid continues shifting toward renewable sources, that advantage compounds over time. Auxiliary heat strips, electric resistance elements some heat pump systems use as backup instead of a gas furnace, maintain the all-electric footprint but give up the cost efficiency of gas backup during deep cold.
Getting the Right Answer for Your Specific Home
A home’s insulation level, window quality, square footage, duct condition, and existing equipment all affect which system will perform best and cost least over time. A load calculation, not a general recommendation, is what actually produces an accurate answer. The right system for a well-insulated 1,800-square-foot ranch with good ductwork isn’t necessarily the right system for a drafty two-story with aging ducts and high ceilings.
Martin-Jetco Heating and Air Conditioning has NATE-certified technicians who evaluate the actual home, recommend only what it needs, and work with leading equipment brands including York, Goodman, Daikin, Carrier, and Trane to match the system to the job. Give us a call at (636) 205-1631 or message us online and we can walk through your specific situation before winter settles in.