Cost of furnace replacement in New Hampshire (NH)
A 100,000 BTU furnace installed
$5,500to $8,300
That is a standard 80% AFUE model, the federal minimum and what most replacements are. A 96% condensing furnace runs $6,600 to $9,800.
Is the efficient one worth it here?
Costs more
$1,300
Saves a year
$522
Pays back in
2.5 yrs
New Hampshire burns enough gas over a winter for the efficiency to earn its premium back well inside the furnace's life. At $2.37 a therm and 7,000 heating degree days, the condensing model is the better buy.
Before you replace like for like
A furnace is not the only option. A heat pump does the same job using electricity, and in some states costs less to run — it depends on the gap between gas and electricity prices where you live, which is not the same everywhere.
Compare both in New HampshireCommon questions
How much does it cost to replace a furnace in New Hampshire?
Between about $5,500 and $8,300 installed for a standard 80% AFUE furnace, or $6,600 to $9,800 for a 96% condensing model. A 1,800 square foot home in New Hampshire needs roughly 100,000 BTU of output.
Is a high-efficiency furnace worth it in New Hampshire?
Yes. The condensing model costs about $1,300 more and saves roughly $522 a year on gas at New Hampshire prices, so it repays itself in about 2.5 years — well inside the life of the furnace.
What size furnace do I need?
About 100,000 BTU for 1,800 square feet in New Hampshire's climate — roughly 56 BTU per square foot, which reflects 7,000 heating degree days a year. Colder states need more output for the same house.
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Sizing from New Hampshire's heating degree days for a 1,800 square foot home. Gas price from the US Energy Information Administration, 2026-05. Installed costs are a national estimate spread ±20% — ductwork, venting runs and your region move real quotes more than the furnace itself does. Get three.