What the number covers
That $6,000 to $12,000 is the installed price, not just the box. It covers the furnace itself, pulling the old unit, the gas and venting connections, and testing the system before I leave. Where your job lands in the range comes down to a few things.
- Size and efficiency. A larger home or a high-efficiency condensing furnace costs more than a mid-efficiency unit for a small ranch.
- Ductwork and venting. If the existing ducts or the venting need work, that adds labor and material.
- Fuel and setup. A clean gas swap is simpler than reworking an old oil setup or moving the unit to a new spot.
- Access. A tight crawlspace or a hard-to-reach attic unit takes longer than a basement swap.
These ranges match the region. Paul the Plumber, over in Derry in the same county, publishes a furnace replacement quick answer of $7,500 to $12,000, and a real Derry job came in around $9,600. My $6,000 floor reflects the simpler straight swaps I do without padding the quote.
Why timing is the whole game
A furnace that dies in a January cold snap is a no-heat emergency at the worst possible price. When the temperature drops and every furnace in the county is failing at once, you are negotiating from panic, paying rush rates, and taking whatever unit is on the truck. Replacing a tired 15-year-old furnace on your own schedule, in the fall, is how you stay out of that trap and actually shop the price.
What NHSaves takes off
New Hampshire NHSaves program pays roughly $300 to $450 on a qualifying high-efficiency gas furnace with an ECM blower. The federal 25C credit that used to apply expired December 31, 2025, so there is no federal furnace credit in 2026, and any page still advertising one is out of date. If you are open to it, a cold-climate heat pump can qualify for much larger NHSaves money, up to $1,250 per ton replacing electric heat, and I will lay out both paths. (NHSaves.com)
Repair or replace?
If your furnace is under about 12 years old and the repair is small, fixing it can be the right call. Once it is 15-plus years old, short-cycling, or facing an expensive part like a heat exchanger or control board, replacing it before it fails in the cold usually costs less over the long run. I give you the honest math, not a scare tactic, and I put the number in writing for free.
