How much does a gas furnace cost to install?

What a new gas furnace actually costs

Sticker prices online quote the furnace box alone, which runs roughly $1,500 to $5,000 at the distributor depending on size and efficiency. That is never the number on your quote, because the box is only about 60 percent of the job. Labor, venting, the thermostat, permits, and hauling away the old unit fill in the other 40 percent. A homeowner who budgets off the online furnace price is usually short by several thousand dollars.

For a standard furnace replacement on usable ductwork, most homes pay $4,500 to $7,500 all-in. The full range runs from about $3,000 for a basic 80% efficiency unit in an easy swap up to $12,000 for a high-efficiency modulating furnace that needs new venting. Where you land comes down to the efficiency tier you pick, the size your home needs, and the condition of the house, which the rest of this guide walks through. Getting the BTU size right before you price anything keeps you from overpaying for capacity you do not need. If you are not yet sure the furnace needs replacing, our guide on the signs you need a furnace replacement covers lifespan and when a repair stops making sense.

Gas furnace prices by efficiency: 80% vs 90% vs 96%

AFUE is the share of fuel a furnace turns into heat. An 80% furnace sends 20 percent up the flue. A 96% furnace wastes only 4 percent. The higher number costs more two ways, and most cost guides only mention the first one.

• 80% AFUE (standard): $3,000 to $6,500 installed. Vents hot exhaust up a metal flue or chimney. The cheapest furnace to buy and install.
• 90 to 95% AFUE (condensing): $4,500 to $9,000 installed.
• 96 to 98% AFUE (high-efficiency, often two-stage or modulating): $6,000 to $12,000 installed.

The second cost is the one quotes hide. Any furnace above about 90% is a condensing furnace, and it cannot vent up a hot metal flue. It runs cool enough that the exhaust turns to liquid, so it needs PVC pipe out a sidewall and a condensate drain or small pump to carry the water away. In a home that currently vents up a chimney, adding that PVC venting and drain runs an extra $500 to $1,800 on top of the higher equipment price. Going the other way, a new 80% furnace put on an old masonry chimney may need a stainless liner, which is $600 to $2,000. Either path has a venting cost most homeowners never see coming.

Whether the high-efficiency furnace earns back that extra cost depends on your climate and gas rate. The jump from an 80% to a 96% furnace runs $1,500 to $2,500 more upfront, and it pays back through lower gas bills in roughly four to seven winters in a mixed climate, faster in a cold one where the furnace runs hard all season. In the warm South, where the furnace barely runs, that payback can stretch past the life of the unit, and an 80% furnace is often the smarter buy. The AFUE payback calculator runs the break-even at your gas rate and heating load.

What size furnace you need, and what it costs

Furnace size is set by your home's heating load on the coldest day, not square footage alone. A rough guide is 30 to 40 BTU per square foot in a warm climate and 45 to 60 in a cold one. That is why the same size house costs more to heat in the North: a Minnesota home might need a 120,000 BTU furnace where a Georgia home of the same size needs 60,000. Bigger furnaces cost a few hundred dollars more in equipment, but the real regional swing is that cold-climate homes lean harder on the furnace and tend to buy up into higher efficiency, while in much of the South the furnace is a secondary appliance behind the air conditioner.

The mistake that actually costs money is buying too big. An oversized furnace short-cycles, blasting on and off, which wears the ignition and gas valve and leaves rooms unevenly heated. A right-sized furnace runs longer, quieter cycles. Run the furnace sizing calculator for your square footage and climate so you can check whatever size a contractor proposes.

Size barely moves the bottom line because of how the cost splits. On a typical furnace swap the furnace itself is around 60 percent of the total and the labor, venting, and permits are the other 40 percent. A bigger furnace costs a few hundred dollars more in equipment, but the crew spends the same day installing it, so jumping up a size class is cheap compared with the things that actually add labor: new venting, a gas line, or ductwork. That is why two homes of different sizes can get surprisingly close quotes while two identical homes get very different ones.

Single-stage, two-stage, or modulating: what each one costs

Burner staging is the other price lever, separate from efficiency. A single-stage furnace runs full blast or off. A two-stage furnace has a high and a low fire, so it runs gentler most of the time and is quieter and steadier. A modulating furnace varies its flame continuously for the most even heat. Two-stage adds roughly $500 to $1,500 over a single-stage unit. Modulating adds the most, and it almost always comes bundled into the top 96%+ efficiency models, which is part of why those high-efficiency jobs reach $10,000 and up.

For most homes a single-stage or two-stage 90%+ furnace is the sweet spot. Modulating earns its premium in cold climates, large homes, or where someone in the house is sensitive to temperature swings and noise. Paying for modulation in a mild climate is money that will not come back in comfort or savings.

What the labor and add-ons run

Labor on a straightforward furnace swap is $1,000 to $2,600, more when venting or ductwork is involved, and the job takes most of a day. The base quote covers the unit and a standard changeout. These add-ons are where a clean price grows, and any of them can be legitimate depending on your home:

• New venting or chimney liner: $300 to $1,200 for PVC on a condensing furnace, $600 to $2,000 for a chimney liner on an 80% unit.
• Gas line work: $400 to $2,000 if the line needs a new run or has to be upsized for a larger furnace.
• Smart thermostat: $150 to $500 installed, plus about $150 if a common wire has to be run.
• Permits and inspection: $100 to $500, more in strict-code cities. A contractor who skips the permit is a red flag, not a discount.
• Electrical: $175 to $800 if the furnace needs a new circuit or disconnect.
• Old furnace removal: $50 to $400 to pull and dispose of the old unit.
• Ductwork modifications: $500 to $3,000 for minor repairs, more for a full reduct.

Get these itemized before you sign. A quote that buries "venting and electrical as needed" without a number is the one that surprises you mid-install.

Why two contractors quote $4,000 and $9,000 for the same house

You can get three quotes for a furnace on the same house and see a spread of several thousand dollars. It is almost never one contractor gouging you. Each one scoped the job differently. The big drivers:

• Efficiency tier: one quoted an 80% furnace, another a 96% condensing unit. That choice alone can move the price $3,000 before anything else.
• Staging: a single-stage box and a modulating one are both "a furnace" on a quote and differ by thousands.
• Venting: moving from 80% to a condensing furnace means new PVC venting and a drain. One contractor priced it in, another quoted the cheaper like-for-like swap.
• Ductwork and gas line: one reused what was there, another priced in repairs after actually looking.
• Brand tier and overhead: a premium brand and a larger company with a sales team both carry more cost than a value brand from a two-truck shop.

The fix is to make every quote describe the same job. Ask each contractor to write down the furnace model and AFUE, the staging, the venting plan, and any gas, electrical, or duct work as separate lines. Then you are comparing the same furnace, not three different ones. The HVAC replacement cost calculator gives you a line-item baseline to hold the quotes against.

Furnace now, or furnace and AC together?

If your air conditioner is also near the end of its life, replacing both at once usually saves $750 to $1,000 over doing them in separate visits, because the crew is already there and the labor overlaps. The bigger reason to think about it is the coil. Your AC's indoor coil sits right on top of the furnace, and the two work as a matched set. Putting a new furnace under an old, mismatched coil can drag down efficiency and complicate the next AC replacement.

If the AC is young and healthy, replace the furnace alone and keep the coil. If the AC is also 10 to 15 years old, getting both quoted together is worth doing even if you only act on the furnace now. Our guide on whether to replace the AC and furnace together walks through the age-gap rule and the matched-coil catch in detail, and the repair or replace calculator helps you decide whether the older half is worth keeping.

What oil, propane, and electric furnaces cost instead

Natural gas is the most common and usually the cheapest fuel to run, but not every home has a gas line. If you are weighing other fuels, here is roughly what each runs installed:

• Propane furnace: $3,000 to $12,000, similar hardware to a natural gas furnace and a similar install, but propane costs more per unit of heat to run.
• Oil furnace: $2,650 to $10,000, the most expensive equipment tier, and oil heat carries higher fuel and maintenance costs along with a tank to keep filled.
• Electric furnace: $1,500 to $7,000, the cheapest to install because there is no flue, gas line, or combustion to deal with, but the most expensive to run in most climates.

The cheap install on an electric furnace is misleading, because resistance heat is costly everywhere power is not dirt cheap. In most of the country a heat pump beats an electric furnace on running cost by a wide margin, which is why the real fuel decision for a no-gas home is usually heat pump versus propane or oil, not which furnace. The heat pump vs gas furnace calculator runs that comparison at your local rates.

Can you still buy an 80% furnace? The efficiency rules explained

Yes. As of now the federal minimum is 80% AFUE nationally, and you can still buy and install a standard non-condensing furnace. You may have read that northern states require a 90% furnace. That rule was proposed years ago, struck down in court, and never took effect, so ignore it.

There is a newer rule on the way. The Department of Energy finalized a standard requiring roughly 95% AFUE, which effectively means condensing furnaces, for units manufactured on or after December 18, 2028. It governs what manufacturers can build, not a ban on installing existing inventory. That rule is also unsettled. The Supreme Court sent it back to a lower court for reconsideration in mid-2026, and the DOE has floated delaying it, so the 2028 date is the current target but not a certainty. The practical takeaway for a purchase today: every tier is still available, and an 80% furnace remains a legitimate buy where a chimney makes condensing venting expensive.

Red flags in a gas furnace quote

Before you sign, watch for these:

• No size justification: a contractor who quotes a furnace size off the old unit's nameplate without measuring your home is guessing. Ask for a heat-loss calculation.
• No permit: a gas appliance install needs a permit and inspection. Skipping it puts the liability and any future insurance claim on you.
• Vague extras: "venting and gas line as needed" with no dollar figure is an open-ended bill.
• Pressure to oversize: bigger is not better with furnaces. An oversized unit short-cycles and wears out faster.
• One quote: get three. The spread on the same house is normal and it is the only way to see who scoped the job honestly.

Run the heat loss calculator before the contractors arrive so you have your own size number to check theirs against, and get three quotes so you can see who scoped the job honestly.