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Cost guide

Furnace Replacement Cost

Replacing a gas or propane furnace while keeping the existing air conditioning system.

Typical range
$2,500–$8,000
Most people pay
$4,500
Service life
15–20 years for a gas furnace

National cost range

National range, per furnace installed

$2,500 – $8,000

Most homeowners pay around $4,500. The spread is real, not hedging — the drivers below determine which end of it you land on.

Low end
$2,500
Simple access, like-for-like
Typical
$4,500
What most jobs come in at
High end
$8,000
Upgrades, difficult access, code work

What you are actually paying for

Find the row that matches your situation. Quotes that differ wildly from each other usually differ in scope, not in price.

ScenarioTypical cost
80% AFUE, like-for-like replacementUses existing metal venting.$2,500–$4,000
95% AFUE condensing furnaceNew PVC venting and condensate drain required.$3,500–$6,000
95% AFUE plus new venting and gas lineCommon when upgrading efficiency from 80% to 95%.$4,000–$7,000
Variable-speed ECM furnaceQuieter, more efficient blower; pairs well with central AC.$4,500–$7,500
Propane furnace in rural areaSimilar to gas but propane tank and regulator must be verified.$3,000–$5,500

What moves the price

In descending order of impact. These are also the questions worth asking a contractor whose quote sits outside the range above.

  1. Efficiency rating (AFUE)

    An 80% AFUE furnace is the minimum and cheapest. A 95 to 98% condensing furnace costs $1,000 to $2,000 more but saves $200 to $400 per year in fuel.

  2. Capacity (BTU input)

    Oversizing is as harmful as undersizing. A Manual J calculation determines the correct input rating. Most homes need 60,000 to 100,000 BTU.

  3. Venting change

    High-efficiency condensing furnaces require PVC venting and a condensate drain. Converting from metal B-vent to PVC adds $300 to $800.

  4. Gas line and code upgrades

    A new gas shutoff, sediment trap, and combustion air requirements may be triggered by the replacement.

  5. Duct connection and plenum

    A deteriorated plenum or transition at the furnace connection may need replacement during the swap.

Can you do it yourself?

Not a DIY job

Furnace installation involves gas piping, combustion venting, electrical connections, and combustion analysis. Carbon monoxide from improper installation is lethal. Licensed HVAC work with a permit is required.

Permits and inspection

A mechanical permit is required. The inspector verifies venting, gas connections, combustion air, and condensate drainage on high-efficiency units.
Run the DIY vs. pro decisionCheck a quote you already have

When this cannot wait

  • Cracked heat exchanger — shut the furnace down immediately
  • Furnace over 18 years old with a major component failure
  • Yellow or flickering burner flame indicating incomplete combustion
  • Carbon monoxide detector alarming near the furnace

Common questions

How much does a new furnace cost installed?
An 80% AFUE gas furnace runs $2,500 to $4,000 installed. A 95% high-efficiency condensing furnace runs $3,500 to $6,000. Variable-speed models run $4,500 to $7,500.
Is a 95% efficient furnace worth the extra cost?
In cold climates with high gas usage, the $1,000 to $2,000 premium pays back in 5 to 8 years through fuel savings of $200 to $400 annually. Federal tax credits up to $600 for high-efficiency furnaces reduce the premium further.
How long does furnace replacement take?
A straightforward like-for-like swap takes 4 to 8 hours. Upgrading to a condensing furnace with new PVC venting takes a full day. Gas line or duct modifications add time.
Should I replace my furnace and AC together?
If the AC is under 10 years old and the furnace is failing, replace the furnace alone. If both are over 15 years, replacing together saves on labor and ensures a matched system. A mismatched coil and furnace reduces efficiency.
Furnace blowing cold air in winter — emergency replacement cost?
Emergency gas furnace replacement runs $3,500 to $6,500 installed. Same-day install is possible for common sizes (60,000 to 100,000 BTU). After-hours labor adds $200 to $500. A failed ignitor ($150 to $300) or flame sensor ($100 to $200) may be the actual fix — get diagnosed before authorizing replacement.
Furnace making a loud bang when it starts — replace cost?
Banging on startup often means delayed ignition from a dirty burner ($150 to $300 cleaning) or cracked heat exchanger (replace furnace at $3,500 to $6,500). A cracked heat exchanger is a carbon monoxide risk — shut the furnace off and call for inspection immediately.
Carbon monoxide detector went off — furnace replacement cost?
Shut off the furnace and ventilate immediately. A cracked heat exchanger requires furnace replacement at $3,500 to $6,500 — repair is not an option. CO detector alerts are life-safety events. Do not restart the furnace until a technician confirms the heat exchanger is intact.
Furnace is 20 years old — repair or replace cost comparison?
Minor repairs under $500 (ignitor, sensor, capacitor) are worth doing. A heat exchanger or blower motor over $1,000 on a 20-year-old furnace should trigger replacement at $3,500 to $6,500. A 20-year-old furnace at 80% AFUE wastes $200 to $400 per year versus a 95% unit.
How much to replace the furnace only and keep the existing AC?
Furnace-only replacement runs $2,500 to $6,000 depending on efficiency. Keeping a functioning AC (under 10 years) saves $4,500 to $8,500 versus full system replacement. Ensure the new furnace coil is matched to the existing AC for rated efficiency.
Furnace pilot light won't stay lit — replacement vs. thermocouple cost?
Thermocouple replacement: $150 to $250. Gas valve replacement: $250 to $450. If the furnace is over 15 years old and the pilot issue recurs, replacement at $3,500 to $6,500 is more reliable than stacking repairs on aging combustion components.

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