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Furnace replacement: what drives the cost

Furnace quotes differ mostly on efficiency and on how much of the old installation can stay.

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The short version

What sets the price
The efficiency rating, the size and the venting the new furnace needs.
The number to know
AFUE: the share of the fuel's energy that becomes heat for the house.
Ask first
Whether the existing vent and ducts can be reused.

Smell gas, or is a carbon monoxide alarm sounding? Leave the house first. Call your gas company or 911 from outside. Do not switch anything on or off on the way out.

A quote should spell out

  • The model number, the capacity and the AFUE rating.
  • How the size was calculated for the house.
  • What happens to the venting and the gas line.
  • Who pulls the permit and books the inspection.

What pushes the price up

  • A high-efficiency furnace that needs new venting and a drain.
  • Ducts that need repair or resizing.
  • Moving the furnace to a new location.
  • Bringing gas piping or wiring up to current code.

What the rating and the house decide

  • AFUEThe Department of Energy's example: an AFUE of 90% means 90% of the energy in the fuel becomes heat for the home.
  • DuctsThe rating leaves out duct losses, which the Department says can be as much as 35% of the furnace's output when ducts run through an attic or garage.
  • SizeA new furnace should be sized to the house as it is now, including any insulation or window work done since the old one went in.
  • VentingHigher-efficiency furnaces vent differently from older ones. The quote should say what changes.

How the job usually goes

  1. A visit to measure the house and inspect ducts, venting and gas line.
  2. A written quote with equipment, scope and price.
  3. The permit, then removal of the old furnace and installation.
  4. Start-up, a combustion and safety check, and the inspection.

This page gives no dollar figures on purpose. Fuel type, efficiency level and local labor rates move the number too much for a national average to help.

Related guides

Sources

  • US Department of Energy
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