For a typical home of 1,500 to 2,500 square feet, OniFix's current ranges for a furnace replacement are $4,500 to $7,500 for natural gas, $4,500 to $8,000 for propane and $6,000 to $10,000 for oil. Choosing a high-efficiency model adds roughly $1,500 to $3,500, which puts a high-efficiency gas furnace in that size of house at about $6,000 to $11,000.
Home size moves the base figure: about 15 percent lower under 1,500 square feet, 20 percent higher from 2,500 to 3,500, and 40 percent higher above that. A standard gas furnace for a 3,000 square foot house, for example, typically runs $5,400 to $9,000. These are typical ranges for a fairly direct swap, not a quote. The exact price depends on what a technician finds at your house, and you get it before any work starts. Here is what pushes a job toward one end of the range, or past it.
Gas, propane or oil: why the fuel changes the price
Natural gas heats a little under six in ten homes in the towns west and north of Boston, according to Census Bureau survey data, so a gas furnace is the most routine version of this job, with the widest choice of equipment.
A propane furnace is, in most cases, a gas furnace set up for propane with the manufacturer's conversion kit, which is why its range sits so close to natural gas. The tank is normally a separate matter between you and your propane supplier and isn't part of the furnace job.
Oil furnaces cost more to replace. The job involves more than setting the unit: the oil line and filter, the flue connection to the chimney, and the combustion testing that sets up the burner to run cleanly. About one home in five in the area still heats with oil, and far more than that in towns like Sherborn. If your oil furnace is due for replacement, it's a natural moment to look at the alternative, and our guide to choosing between a heat pump and a furnace walks through that decision.
Standard or high efficiency: what changes besides the label
Furnace efficiency is rated as AFUE, the share of the fuel's energy that ends up as heat in your house over a season. A standard gas furnace is around 80 percent AFUE, so about a fifth of what you pay for is lost, most of it up the chimney. A high-efficiency furnace is rated at 90 percent or more, and ENERGY STAR sets its bar for gas furnaces in the northern U.S. at 97 percent. These furnaces get there with a second heat exchanger that pulls extra heat out of the exhaust, cooling it so much that the water vapor in it condenses. That's why they're called condensing furnaces.
The cooler exhaust changes the installation. A condensing furnace vents through plastic pipe (usually PVC, sometimes CPVC or ABS, as the manufacturer specifies) instead of a metal flue into the chimney, and it often has a second pipe that brings combustion air in from outdoors. Both run out through a wall or the roof. The furnace also produces a steady trickle of mildly acidic condensate, which needs a floor drain close by or a condensate pump to carry it away. With a drain beside the furnace and an outside wall a few feet away, this adds little. In a finished basement, or when the nearest usable wall is across the house, the vent run and the price both grow.
The chimney question when a water heater shares the flue
The cost people miss most often involves the chimney. In many older homes, an 80 percent gas furnace and a gas water heater vent into the same chimney. When the furnace switches to plastic venting, the water heater is left alone in a flue that was sized for two appliances. The Department of Energy's installation guidance for high-efficiency gas furnaces says the venting for the remaining appliance has to be rechecked against the code venting tables, that an exterior masonry chimney will need a liner, and that overlooking this step leads to underestimating the cost of the replacement.
The concern is practical. A small water heater can't keep a large, cold chimney warm enough to draft reliably, so its exhaust can linger, condense inside the masonry and, in a bad case, spill back into the basement. A liner sized for the water heater solves that. A good quote either includes the liner or explains why your chimney doesn't need one.
Is high efficiency worth the extra cost?
It comes down to how much fuel you burn and how long you'll own the house. A Massachusetts heating season is long, so in a large or drafty house the gap between 80 and 95-plus percent adds up quickly. In a small, tight house, or one you expect to sell in a few years, a standard furnace can be the more sensible buy. Oil is a different case: condensing oil furnaces are uncommon, and ENERGY STAR's threshold for oil furnaces is 87 percent AFUE, so ask exactly which rating you're getting for the higher-efficiency price.
Sizing should come from a heat load calculation
Many older furnaces are bigger than the house needs, either because they were sized generously from the start or because the house has since gained insulation, better windows or air sealing. Replacing size for size carries the mistake forward. An oversized furnace runs in short bursts, which means wider temperature swings, more wear on parts and more noise. The better approach is a heat load calculation (ACCA's Manual J is the industry standard) based on the house itself: its size, insulation, windows, air leakage and orientation. The answer is often a smaller furnace than the one coming out, and a smaller furnace usually costs less.
Single-stage, two-stage and modulating furnaces
At the same efficiency rating, furnaces still differ in how the burner runs. A single-stage furnace is either fully on or off. A two-stage furnace spends most of the winter on a lower setting and goes to full fire only on the coldest days, which gives longer, quieter cycles and steadier temperatures. A modulating furnace adjusts its output in small steps to match what the house is losing at that moment. Each step up costs more, and the better models usually come with a variable-speed blower, which also helps if the furnace moves air for central AC. For many homes two-stage is the practical middle ground, while modulating earns its price where uneven comfort is the real complaint.
The parts of the job beyond the furnace itself
Much of the gap between a low and a high price sits in the work around the furnace rather than the furnace itself.
Ductwork, the plenum and the air conditioning coil
A new furnace rarely has the same footprint as the old one, so the sheet metal that connects it to the supply and return ducts (the plenum and transitions) usually gets rebuilt. An undersized return, common in older systems, may need enlarging so the new furnace gets enough air. If you have central air, its indoor coil sits on top of the furnace and has to line up with the new cabinet. When the air conditioner is near the end of its own life, price the two together: the coil and the outdoor unit work as a matched pair, and replacing them on a separate visit means redoing the same sheet metal.
Where the furnace sits
A furnace in an open basement with a clear path to the door is the straightforward case. Attic furnaces, which some houses have for a second-floor system, take more labor: the equipment comes through a hatch or pull-down stairs, it's installed horizontally, and in a cold attic the condensate lines need protection from freezing. Closets and tight utility rooms limit which models fit and leave less room to work.
Gas connection, permits and inspection
In Massachusetts, gas fitting work can only be done under a permit issued to a licensed plumber or gas fitter, and the local gas inspector has to sign off on the installation. If the furnace needs a new circuit or service switch, that work belongs to a licensed electrician working under a wiring permit. Permit fees vary by town and are usually a small part of the total, but a quote that never mentions permits deserves a question.
Removing the old furnace
Taking out and hauling away the old furnace is normally part of a replacement, though it's worth confirming. In older houses, look at the insulation on the ducts and pipes around it. If it might contain asbestos, it should be tested before anyone disturbs it, and removing it is specialized work that's priced on its own.
The thermostat
A single-stage furnace works with almost any thermostat. Two-stage and modulating furnaces need one that can call for both stages, and some modulating systems use the manufacturer's own communicating control. If you want a new thermostat as part of the job, make sure it's written into the quote.
Rebates and tax credits for a new furnace in 2026
There isn't much to subtract this year. The federal Energy Efficient Home Improvement Credit, which allowed up to $600 for a qualifying gas or oil furnace, ended with 2025, so a furnace installed in 2026 doesn't qualify. Mass Save no longer offers rebates or financing for equipment that runs on natural gas, oil or propane, a change tied to the state's 2021 climate law. The exception is income-eligible households: Mass Save still offers them incentives to upgrade existing fossil fuel equipment to high-efficiency models. The 0% HEAT Loan currently covers heat pumps, weatherization and a short list of other improvements, but not furnaces.
When repairing the old furnace makes more sense
Replacement isn't always the right call. OniFix's typical furnace repairs run $350 to $1,500, and a furnace under ten years old with a failed igniter, inducer motor or control board is usually worth fixing. A useful rule of thumb: a furnace over 15 years old is close to the end of its usual life, and once a repair on it costs more than $1,500, replacing it is sometimes the better choice. A cracked heat exchanger in an older furnace is the classic example: the repair is expensive and everything around it is just as old. Our guide on deciding whether to repair or replace goes through the decision, and the article on how long a furnace lasts covers the signs that one is wearing out.
Getting furnace quotes you can actually compare
Because so much of the price lives in venting, ductwork, sizing and the chimney, two quotes for what sounds like the same job can be thousands of dollars apart. Ask each contractor for model numbers, the AFUE rating, how they sized the furnace and what's included, then compare line by line. Our article on how to compare HVAC quotes has the full checklist, and the furnace replacement page walks through the job itself, from the first look at your system to the test run at the end.
For a range based on your own fuel, efficiency choice and home size, open the instant price tool. It takes about a minute, and the exact figure comes after a technician sees the furnace, before any work starts.
Sources: IRS, Energy Efficient Home Improvement Credit; Mass Save, boilers and furnaces; Mass Save, HEAT Loan; U.S. Department of Energy, Measure Guideline: High Efficiency Natural Gas Furnaces; ENERGY STAR, furnace criteria; 248 CMR 3.00, plumbing and gas fitting work; Mass.gov, electricians consumer fact sheet.