Most people start shopping for a furnace with one question, and it isn’t about efficiency ratings or brand reputation. It’s “what is this going to cost me?” That number is hard to pin down online, because almost every price you find is a national average built from markets that don’t share Denver’s altitude, code requirements, housing stock, or labor rates.
Here’s a straight answer, written as ranges rather than a single number, because a furnace replacement isn’t one product. It’s equipment plus the work required to make that equipment fit your house legally and safely. L & L Heating and Air Conditioning has been replacing furnaces across the Front Range for more than three decades, and the spread between the cheapest job and the most expensive one in the same neighborhood usually comes down to six specific things, all of which are covered below.
A note on the numbers: the ranges on this page reflect installed pricing in the Denver metro as of fall 2026. They are ranges, not quotes. Your actual price depends on the equipment selected, the condition of your existing venting and ductwork, gas and electrical requirements, access to the equipment, permit fees in your jurisdiction, and prevailing material and labor costs, all of which move. Treat this as a budgeting framework, then get a written estimate for your specific home.
Furnace Replacement Cost in Denver by Equipment Type
Furnace pricing scales with two things: how the burner fires, and how the exhaust leaves the building. Those two decisions drive most of the equipment cost difference.
80% AFUE Single-Stage Furnace
Typical installed range: $4,500 to $7,500
This is the baseline replacement. The burner is either on at full output or off, and combustion gases vent through an existing metal flue, usually the same chimney or B-vent the old furnace used. When the existing venting is in good condition and sized correctly, this is the least disruptive swap available, and it’s why the low end of this range exists at all.
80% AFUE Two-Stage Furnace
Typical installed range: $5,500 to $9,000
Same venting story, better comfort behavior. The burner has a low fire and a high fire, so the furnace spends most of a mild Denver day running gently instead of blasting and shutting off.
96% AFUE Single-Stage Condensing Furnace
Typical installed range: $6,500 to $10,500
The efficiency jump comes with a venting change. A condensing furnace can’t use a metal flue, because it pulls so much heat out of the exhaust that the gases cool and condense. It needs new PVC pipe routed to an exterior wall or roof, plus a drain for the condensate it produces. In a 1950s Denver ranch with a center-of-basement furnace and no easy exterior wall, that routing is the line item that surprises people.
96% AFUE Two-Stage Condensing Furnace
Typical installed range: $7,500 to $12,000
The most common recommendation for a mid-size Denver home that plans to stay put. High efficiency plus staged firing, with the same PVC venting and condensate requirements as above.
Modulating Furnace with Variable-Speed Blower
Typical installed range: $9,500 to $15,000 and up
The burner adjusts its output continuously rather than in steps, and the blower ramps with it. This is the quietest and most even option available, and it’s also the one most often sold to homes that won’t perceive the difference.
Furnace Cost by Home Size
Sizing is not a matter of square footage alone, and at Denver’s elevation it’s genuinely a technical calculation rather than a rule of thumb. Gas furnaces lose roughly 4% of their rated output for every 1,000 feet above sea level, so a furnace sized by a sea-level chart will be undersized here. The correct method is a Manual J load calculation, and the reasons that matters are covered in detail in our guide to high-altitude furnace sizing.
That said, size correlates loosely with cost, because larger homes need larger equipment and often more extensive ductwork:
| Home size | Typical furnace input | Common installed range |
| Under 1,200 sq ft | 40,000 to 60,000 BTU | $4,500 to $8,500 |
| 1,200 to 2,000 sq ft | 60,000 to 80,000 BTU | $5,500 to $11,000 |
| 2,000 to 3,000 sq ft | 80,000 to 100,000 BTU | $6,500 to $13,000 |
| 3,000+ sq ft or two systems | Varies, often dual furnaces | $12,000 to $25,000+ |
The wide spread inside each row is the point. Two identical 1,800-square-foot homes three blocks apart can quote $6,000 apart, and the reason is never the thermostat.
The Six Things That Actually Move the Number
When two estimates for the same house differ by thousands, it’s almost always one or more of these.
1. Venting Changes
Moving from an 80% furnace to a 96% furnace means abandoning the metal flue and running new PVC intake and exhaust to the outdoors. Typical add: $600 to $2,000, depending on how far the pipe has to travel and whether it can be routed through finished space without demolition.
There’s a second wrinkle specific to older homes. If your furnace and your water heater currently share a chimney, pulling the furnace off that chimney leaves the water heater venting alone into a flue now oversized for it. That can cause draft problems and condensation inside the chimney, and correcting it sometimes means relining the flue or changing the water heater. Any estimate that converts you to high efficiency without addressing an orphaned water heater has left something out.
2. Gas Line Sizing
A higher-input furnace, or a furnace moved to a new location, may need a larger gas line or a new branch run. Older homes with undersized piping and several gas appliances hit this regularly. Typical add: $350 to $1,500.
3. Electrical Work
Modern furnaces need a dedicated circuit and a service switch. Variable-speed equipment is fussier about grounding and neutral quality than an old single-speed blower ever was. If your panel is full, or the existing circuit is shared, expect work. Typical add: $300 to $2,500, the high end being panel-level work.
4. Duct and Return Air Condition
This is the most commonly skipped item and the one that most often ruins an otherwise good installation. A new high-capacity furnace pushing air through undersized returns will run hot, cycle on its limit switch, and wear out early. Undersized return air is endemic in Denver’s older housing stock, and we’ve written about why return air sizing is crucial in Denver because it’s the root cause behind so many “new furnace, same problems” calls. Typical add: $500 to $3,500 for return additions, transitions and sealing.
5. Efficiency Tier
Covered above in the equipment ranges, but worth restating as a driver rather than a product: the choice between 80% and 96% doesn’t just change the box, it changes the venting, the drainage, and sometimes the chimney. The equipment gap between the two is smaller than most homeowners assume. The installation gap is larger.
6. Access
A furnace in an open basement with a floor drain nearby is a straightforward day. A furnace in a knee-wall attic, a crawlspace, or a closet with a 28-inch door is not. Access affects labor hours, and occasionally it affects what equipment will physically fit. Typical add: $300 to $1,200.
What Quotes Routinely Leave Out
Comparing two estimates means checking for the items that quietly separate a complete price from an attractive one:
- Permit and inspection. Furnace replacement requires a permit across Front Range jurisdictions. Typical: $150 to $500. A quote with no permit line is either absorbing it or skipping it, and you want to know which.
- Condensate drain and pump. Condensing furnaces produce water. If there’s no gravity drain nearby, a pump is required. Typical: $150 to $600.
- Startup and commissioning. Gas pressure set, temperature rise measured against the nameplate, external static pressure checked, combustion verified, altitude derate confirmed. This is the step that determines whether you actually get the efficiency you paid for.
- Thermostat. Staged and modulating equipment needs a compatible thermostat. Typical: $150 to $600.
- Haul-away and disposal.
- Labor warranty. Parts warranty comes from the manufacturer. Labor warranty comes from the contractor, and the two are not the same thing.
- Combustion air. In tighter or partially finished older basements, the furnace needs a verified supply of air to burn safely. Our article on combustion air in older Denver homes explains why this gets missed and why it matters.
Repair or Replace, and When to Buy
This page is about the cost of a replacement, not about whether you need one. If you’re still weighing a repair against a new system, that decision has its own framework, and our guide on when to replace versus repair your furnace walks through age, repair frequency and the point where continued repairs stop making financial sense. For a single component failure rather than a whole system, something like a furnace limit switch replacement sits in an entirely different price bracket.
Timing matters too. Replacing a furnace during a January cold snap costs more in stress than in dollars, but it does limit your options on equipment availability and scheduling. Our breakdown of the best time of year to replace your HVAC in Colorado covers the shoulder-season windows worth planning around.
If gas isn’t a given for you, it’s worth looking at whether a dual fuel heat pump makes sense for a Denver home before committing to a furnace-only replacement, since the equipment decision changes the cost structure considerably.
Paying for It
Two things reduce the out-of-pocket number. Manufacturer and utility incentives change year to year, so confirm what’s current rather than relying on last season’s figures. And HVAC financing spreads the cost into monthly payments, subject to credit approval. Current promotions are listed on our coupons page.
Frequently Asked Questions About Furnace Replacement Cost in Denver
Most Denver-area furnace replacements land between roughly $4,500 and $12,000 installed, with modulating high-efficiency systems and large or dual-system homes running higher. The range is wide because venting, gas, electrical and duct conditions vary enormously across the Front Range housing stock. Pricing as of fall 2026 and subject to change with materials, scope and labor.
A 96% AFUE condensing furnace can’t reuse an existing metal flue. It requires new PVC venting run to the exterior and a condensate drain, and in an older home with the furnace in the middle of the basement, that routing is real work. The equipment costs more, but the installation is usually the larger share of the difference.
Yes. Front Range jurisdictions require a permit and inspection for furnace replacement. Permit fees typically run $150 to $500 depending on the jurisdiction, and the contractor should be pulling it, not the homeowner.
A straightforward same-configuration swap is commonly a single day. Converting to high efficiency, adding return air, or performing gas or electrical work extends that, sometimes to two days.
No, and at altitude the question is more complicated than it sounds. An oversized furnace short-cycles, produces uneven temperatures and wears out faster. Correct sizing comes from a Manual J calculation that accounts for Denver’s elevation derate, not from square footage guesswork.
Get a Real Number for Your Home
Ranges are useful for budgeting. They’re not a substitute for someone looking at your venting, your panel, your ductwork, and your gas line. Our team handles furnace and heating installation across the Denver metro, from Arvada to Monument, and every estimate we write itemizes what’s included so you can compare it honestly against anything else on your kitchen table.
Request an estimate, and we’ll put a real number, not a range, in front of you.
