Gas furnace replacement cost, and the venting line most quotes hide

How furnace replacement cost works

1. Size it by output, not by the old plate. Furnaces are sold by input BTU and deliver less than that as heat, so the number to compare is output at the efficiency rating. A load calculation on the house gives the output it needs; matching whatever was there before repeats an oversizing decision somebody else made decades ago.
2. Decide condensing or non-condensing. A condensing furnace extracts more heat and is more efficient, but it vents in plastic through a wall rather than up the chimney and it produces condensate that has to reach a drain. Where neither is easy, a non-condensing furnace can be the cheaper total job even at a lower rating.
3. Ask what happens to the chimney. When a condensing furnace takes the flue out of service, a water heater still sharing that chimney can be left orphaned and unsafe to vent. Fixing that is part of the job and it belongs on the quote, not in a conversation on the day the crew arrives.
4. Check the gas line and the electrical. A larger burner can need a bigger gas line, and a variable-speed blower needs a dedicated circuit and a correctly sized breaker. Both are ordinary work and both are commonly missing from the cheapest bid on the pile.
5. Get the permit and the disposal named. A furnace replacement is normally a permitted job with an inspection, and the old unit has to be hauled away. A quote with neither line is either absorbing them or leaving them for you, and it is worth knowing which before you compare it with anything else.

When the loss pays, and the cost to replace furnace equipment it meets

A furnace that has been under water is not a furnace that can be dried out and restarted: the burner, gas valve and control board are replaced rather than cleaned, and manufacturers say so. That makes a flooded furnace a claim item with a clear position behind it, and the restoration record of the water depth and duration is the evidence the adjuster needs. Age and ordinary wear are not perils and are not covered.

Common questions

How long does a gas furnace last?

Long enough that most replacements are decided by a failure rather than a date. The parts that end a furnace are the heat exchanger, which cannot be repaired safely once it cracks, and the control board and gas valve, which can cost enough on an old unit to make replacement the better spend.

Is a high-efficiency furnace worth it?

It depends on how much heating your climate demands and on what the venting will cost in your house. Where the heating season is long the fuel saving is real; where a condensing furnace needs a new vent route and a condensate drain through finished space, the installed premium can outrun the saving.

Can I keep my old thermostat?

Sometimes. A single-stage furnace works with almost anything; a two-stage or variable-speed furnace needs a thermostat that can call for its stages, and some need a common wire that older installations never ran. Ask whether the quote includes the thermostat and the wiring.

Do I need a permit to replace a furnace?

In most jurisdictions yes, and the inspection is what confirms the venting, the gas connection and the electrical are right. A contractor who proposes to skip it is proposing that you carry the risk of an uninspected combustion appliance in your house.

What moves the cost of furnace replacement most?

The venting. A high-efficiency condensing furnace does not use the old chimney flue; it vents through plastic pipe out of a wall and drains acidic condensate, and routing both through a finished house is real work. After that come the chimney question for a water heater left on the old flue, the gas line and the electrical, and the permit and disposal.

What does a condensing model add to furnace installation cost?

More in installation than a like-for-like non-condensing swap, because the new vent and condensate drain have to be routed and a water heater still sharing the chimney may need its own venting. Where the heating season is long the fuel saving can repay that; ask for both options on one visit.

Claims data by state

• Water damage claims in Arizona
• Water damage claims in Florida
• Water damage claims in Georgia
• Water damage claims in North Carolina
• Water damage claims in Texas
• Water damage claims in Washington