What a Furnace Replacement Actually Costs in the Nashua Area

Last checked: August 6, 2026  •  based on New Hampshire installed-price data and 2026 national cost surveys

The Gap Between the Search Results and Your Driveway

Search what a new furnace costs and you will find numbers that disagree with each other by a factor of five. Some are national averages that quietly include markets where labor runs half of what it does in New England. Some are equipment-only prices with the install stripped out. And some, as we will get into below, appear to be modeled figures that no contractor in this state has ever written on a proposal. What follows is the range that actually shows up on quotes around Nashua, Hudson and Pelham as of August 2026, and the specific things that push a project to one end of it or the other.

The short version: a furnace replacement in New Hampshire — oil or gas — generally runs $4,000 to $9,500 installed as of August 2026. If heating and cooling are both being replaced at once, a complete HVAC system replacement in this state generally runs $5,500 to $18,500 as of the same date. For reference, gas furnaces nationally run about $3,800 to $12,000 installed, with an overall national average near $4,799 as of August 2026 — a useful sanity check, but not a forecast for your street.

Every one of those figures is a range because a furnace replacement is not a product, it is a day or two of work on a specific house. The only thing that produces a real number is a contractor standing in your basement looking at your flue, your ducts and your electrical panel. Nashua HVAC is a referral service: we connect homeowners with licensed, insured local contractors who put that number in writing before anything gets torn out.

Why the Cheapest Numbers You Are Seeing Are Not Real Prices

Several price-aggregator sites currently rank near the top for furnace cost searches in this area, and at least one of them publishes a Nashua figure in the neighborhood of “$1,409 to $1,552” for a furnace replacement. That is not a real installed price anywhere in New England as of August 2026 — on most jobs it would not cover the equipment alone, never mind the labor, the venting, the permit and the haul-away. The tell is the pattern: those same sites publish similarly low, suspiciously narrow ranges for one town after another, which is what scraped or modeled data looks like, not what a stack of actual quotes looks like. Figures in that range typically describe a repair — a control board, an inducer motor, a burner assembly — or a partial job like setting a unit someone else supplied. A homeowner who builds a budget from them is going to hear their first legitimate quote and assume they are being gouged, when in fact they were misled a week earlier by a page that has never had anyone on the ground in this city.

The Real Ranges, and Why Southern New Hampshire Runs High

• Furnace replacement, oil or gas: $4,000 to $9,500 installed in New Hampshire as of August 2026. The spread is mostly your house, not the brand on the box.
• Complete system replacement: $5,500 to $18,500 as of August 2026, when heating and cooling are done together or when the project involves ductwork, a fuel change or a full mechanical-room rebuild.
• National comparison points: roughly $3,800 to $12,000 installed for gas furnaces, with an overall national average around $4,799 as of August 2026. Treat the national average as a floor, not a target.
• We price like Boston, not like the rest of the state: contractors in this corner of New Hampshire routinely work both sides of the Massachusetts line, so their labor rates, insurance and overhead track the Boston-area market. That is the single most useful thing to understand about pricing here — a statewide or national average will systematically read low for Nashua.
• One thing genuinely in your favor: New Hampshire has no sales tax. On equipment, that is a real 5–7% difference compared with buying the same system in Massachusetts, Maine or Vermont — and it applies automatically, with no form to file.

What Actually Moves the Number on Your Quote

• Fuel type: gas, oil and propane are not interchangeable line items. Oil equipment carries its own venting and tank considerations; propane usually mirrors gas pricing but depends on line sizing and regulator capacity; converting to natural gas adds a service connection if a main is at the street and is a much larger project if one is not.
• Efficiency tier (AFUE): the jump from a mid-efficiency furnace to a 90%-plus condensing model is rarely just a better box. Condensing units vent through PVC out a sidewall instead of up the chimney and need a condensate drain, so the upgrade often brings venting and plumbing work along with it.
• Straight swap versus modifications: same fuel, same location, same capacity, existing venting reused — that is the cheap end of the range and often a one-day job. Relocating the unit, resizing after a real load calculation, or adding a cooling coil for future central air moves you toward the middle and upper end.
• Ductwork condition: undersized returns, crushed or disconnected trunk lines in an old basement, leaky joints, or a 1950s octopus system that was never balanced. A high-efficiency furnace bolted to bad ductwork underperforms permanently, so a good contractor prices the fix rather than ignoring it.
• Venting and chimney work: the most commonly underestimated cost on the whole project, and the reason for the next section.
• The small line items that still add up: the City of Nashua residential mechanical permit runs $50 for application and review plus $45 for the furnace, so $95 as of August 2026 — Hudson and Pelham set their own fees. Add disposal of the old unit, and removal of an oil tank if that is part of the job. Permits and contractor licensing are covered in depth on our separate New Hampshire permits and licensing guide; here they are simply line items you should see itemized rather than buried.

The Chimney Problem Nobody Warns You About

Here is the surprise that blindsides more Nashua-area homeowners than any other. In a lot of older houses, the furnace or boiler and the gas water heater share a single masonry chimney flue, and that flue was sized for the combined exhaust of both appliances. Replace the heating equipment with a high-efficiency condensing unit that vents out the sidewall in PVC, and the water heater is suddenly alone on a flue several times larger than it needs — what the trade calls an orphaned water heater. The consequences are not cosmetic. A small appliance cannot generate enough heat to establish draft in an oversized, cold masonry chimney, so exhaust lingers, moisture condenses on the flue walls, and over time you get deteriorating masonry, staining, and in the worst case combustion gases spilling back into the basement instead of going up. The standard fix is a properly sized stainless steel liner run down the chimney and matched to the water heater's BTU input, and nationally that work commonly falls somewhere around $900 to $3,800 as of August 2026, with New England labor tending toward the upper half of that. The point is not the exact figure — it is that this line item is real, it is common in this housing stock, and a quote that upgrades you to a condensing furnace without addressing what happens to the water heater is an incomplete quote. Ask about it directly before you sign anything.

So What Should You Actually Budget?

An honest answer, with the same caveat attached to every number on this page: these are August 2026 ranges, and only an in-home visit produces a price. If your house is a clean like-for-like swap — same fuel, same spot, venting and ducts in decent shape — plan for the lower half of the $4,000 to $9,500 New Hampshire range and treat anything under that as a signal to read the quote very carefully for what was left out. If you are going to high efficiency, or the chimney needs a liner, or the ductwork needs real attention, budget the upper half and do not be shocked by a number above it. If heating and cooling are both at end of life, you are effectively pricing a system, not a furnace, and the $5,500 to $18,500 complete-replacement range is the relevant one. Then add the permit, and add a genuine contingency — on a fifty-year-old house, some of what matters is behind a wall until the day of the install.

What a Legitimate Itemized Quote Contains

• The specific equipment: manufacturer, model number, BTU input and output, and AFUE rating. “High-efficiency furnace” with no model number is not a specification and cannot be compared against a competing bid.
• The sizing basis: a load calculation for your home, not a number copied off the nameplate of the unit being removed. Oversizing is the most common and most expensive mistake in this trade, and you live with it for twenty years.
• Venting, in writing: what the new unit vents into, what happens to the old flue, and whether a chimney liner is included, excluded, or to be determined after inspection. Vague language here is where surprise invoices come from.
• Everything that is not the furnace: permit fees, electrical work, gas or oil line modifications, condensate drainage, thermostat, duct repairs, and haul-away and disposal of the old equipment.
• Labor, warranty and terms: the labor warranty separate from the manufacturer's parts warranty, who registers the equipment, the payment schedule, and the expected duration of the work.
• What is explicitly excluded: the most trustworthy quotes say plainly what is not included and what would trigger a change order. Three bids only compare honestly when all three cover the same scope — a low bid is often just a smaller job wearing the same title.

When a Heat Pump Belongs in the Comparison

If your furnace is at the end of its life, the useful question is not only which furnace, but whether a furnace is still the right machine. Fuel cost is why: New Hampshire's average price for #2 heating oil sits around $4.71 per gallon as of August 2026, and at that level the annual spread between a tired mid-efficiency unit and a modern high-efficiency one is large enough that the efficiency upgrade often pays for its own venting work over a reasonable horizon. Push the same logic one step further and a cold-climate heat pump enters the conversation, either on its own or paired with the furnace as a hybrid that hands off in the deepest cold — and unlike a furnace swap, that path may carry utility rebates worth real money, which our dedicated New Hampshire heat pump rebate guide covers in current detail. Two honest cautions: the federal 25C tax credit that used to sweeten these projects expired on December 31, 2025 and does not apply to a 2026 installation, and a heat pump is not automatically cheaper to run than gas in every house. Both questions are answerable, but they are answered by load and fuel math on your specific home, not by a range on a web page.

Get a Real Furnace Quote for Your House

Tell us what's going on and a local pro will follow up quickly.

Name * Phone *

The contractor calls this number back — a mobile gets you reached fastest.

Town * Select your town Nashua Hudson Pelham Other nearby What's going on? Request Service

By submitting, you agree that your information may be shared with a licensed local HVAC contractor who will contact you about your service request. See our privacy policy.

In a hurry? Calling is faster than typing — (603) 506-4389.

More HVAC Help Across Greater Nashua

One number covers the whole list — repair, replacement, and the yearly check that prevents both.