Boiler Replacement Cost Calculator
A boiler replacement costs about $10,403 in Boston for a standard gas hot water unit with two zones, and $13,198 for a condensing one. The part nobody sells you: a condensing boiler only condenses if the water coming back is cold enough, and that is decided by your radiators, not by the boiler. Behind old emitters, without an outdoor reset curve, you pay for 95% and run at rather less.
Estimate the cost for your home
Estimated cost to replace the boiler
$9,309
typical · range $6,438 to $12,180 · 120,000 BTU/h · 84% AFUE · 2 zones · 35.5 trade hours
Labour priced at national wages. Enter a ZIP code to price it for your area. 76% of this figure comes from modelled material prices — each line shows its own uncertainty.
Priced from bls.gov Aug 2026how every line is sourced
The one input that changes the answer for you.
The common case. Federal minimum is 84% AFUE for units manufactured since January 15, 2021 — higher than the 80% floor for a warm-air furnace, which surprises people who assume the two are the same appliance in a different shape.
Vents hot into an existing chimney, which in most cases has to be lined for the new appliance because modern boilers put out less waste heat than the one being removed and an oversized flue does not draw. Simple, robust, and what the federal minimum describes.
The default in post-war American houses. Designed around water at roughly 80 °C, so a condensing boiler spends much of the season above its condensing point unless the system is set up with an outdoor reset curve and the boiler is allowed to run cooler for longer. Doable, and it has to be asked for.
The water heater is its own appliance and is not touched. ⚠️ If it shares the chimney with the boiler, read the venting note: taking a boiler off a shared flue leaves the water heater with a flue far too big for it.
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The figure above is already calculated. Each step just makes it more yours, and you can stop at any of them.
A condensing boiler only condenses if the water coming back is cold enough
And that is decided by what heats your rooms, not by the boiler. Same house, same installer, condensing boiler behind three different emitters.
| What heats the rooms | Condenses in normal use? | Cost |
|---|---|---|
| Fin-tube baseboard | Only with an outdoor reset curve | $11,976 |
| Cast-iron radiators | Only with an outdoor reset curve | $12,350 |
| Underfloor radiant | Yes, nearly always | $12,506 |
Going condensing costs $2,667 more here — $11,976 against $9,309. Whether you get that back depends on the middle column. Your emitters were sized for hot water, so without an outdoor reset curve the boiler will run above its condensing point for much of the winter and deliver roughly the efficiency of a standard unit that cost a third less. That control is priced in the breakdown — make sure it is in your quote too, and make sure somebody sets the curve rather than just fitting the sensor.
| Line item | Qty | Cost | Source |
|---|---|---|---|
| Gas boiler, standard efficiencyboiler input BTU ÷ 1,000, gas at standard efficiency | 1201,000 BTU/h input | $2,640–$5,400 | estimated±34% |
| Near-boiler piping and manifold1 per boiler | 1each | $420–$1,100 | estimated±45% |
| Expansion tank, air separator and fill valve1 on any hot water system | 1each | $140–$380 | estimated±46% |
| Circulator pumpsone per zone, on a pumped system | 2each | $260–$680 | estimated±45% |
| Zone valves, manifold and controlsone per zone | 2each | $170–$440 | estimated±44% |
| Lining the chimney for the new boiler1 when a standard-efficiency boiler needs the chimney lined | 1each | $280–$720 | estimated±44% |
| Gas connection, shutoff and sediment trap1 on any fuel-burning boiler | 1each | $55–$140 | estimated±44% |
| Removal, setting and piping24 trade hours, plus 6 on steam and 4 for condensing venting | 24hour | $1,429–$1,536 | sourced |
| Piping and wiring each zone2.5 hours per zone, on a pumped system | 5hour | $298–$320 | sourced |
| Boiler circuit, service switch and controls wiring1 per boiler | 1each | $70–$190 | estimated±46% |
| Electrical connection2.5 hours per boiler | 2.5hour | $147–$158 | sourced |
| Fill, purge, combustion analysis and balancing4 hours on a fuel-burning boiler, 2 on an electric one | 4hour | $238–$256 | sourced |
| Breaking up and removing the old boiler1 when the old boiler is taken away | 1each | $180–$480 | estimated±45% |
| Mechanical permit and inspection1 when the job is permitted | 1each | $110–$380 | estimated±55% |
| Total | $6,438–$12,180 | ±31% |
Where these numbers come from
- The condition that makes the efficiency real
- Going condensing costs $2,795 more here — $13,198 against $10,403. Whether you get it back depends on the return water temperature, which your emitters set. Underfloor radiant runs cool by nature and condenses nearly always: $13,728 on this house, and worth every part of the premium. Fin-tube baseboard and cast-iron radiators were sized for water at roughly 80 °C, and behind those a condensing boiler needs an outdoor reset curve — a sensor outside and a control that lowers the water temperature as the weather mildens — to spend meaningful time below its condensing point. ⚠️ That control is in the breakdown here. Make sure it is in your quote, and that somebody sets the curve rather than just fitting the sensor.
- The federal minimum, which is not the furnace one
- 10 CFR 430.32(e)(2) sets, for boilers manufactured on and after January 15, 2021: 84% AFUE for gas hot water, 82% for gas steam, 86% for oil hot water and 85% for oil steam. Higher than the 80% floor that applies to a warm-air furnace, which surprises people who assume the two are the same appliance in a different shape. The same rule adds a design requirement in as many words: “Constant-burning pilot not permitted” — the permanent standing pilot is gone. Read in the regulation on govinfo, retrieved 2026-08-23.
- Steam, and a product that does not exist
- A gas steam boiler comes to $10,452 here. There is no condensing option for it and there never will be: steam has to be made at boiling point, so the condensate returning to the boiler can never be cold enough to condense the flue gas. That is why its federal floor is 82% rather than 84%. If somebody offers you a 95% steam boiler they are describing something that is not for sale. What genuinely helps a steam system is cheap and unglamorous: correct near-boiler piping, working vents, and running it at ounces of pressure rather than pounds. Steam systems are usually not underperforming because the boiler is old.
- The part of the job you cannot judge by looking
- The near-boiler piping — the fabricated manifold immediately above the boiler that everything else connects to — is made on site, every time, and never the same twice. It is where good work and bad work separate, and a homeowner cannot tell them apart. On a steam boiler it is not cosmetic at all: piped wrong, the boiler carries water over into the mains and hammers, and no amount of efficiency rating fixes that. It is itemised in the breakdown rather than folded into labour so that you can at least see it exists and ask what is being fitted.
- Oil, electric, and what each really costs
- Oil is $12,067 against $10,403 for gas: the burner is a pressure-atomising assembly with its own motor, pump and ignition, and it carries an annual service that is not optional. Electric is $7,598, cheapest to buy by a wide margin and the most expensive way to make heat that exists — the saving at purchase is repaid to the utility with interest, and a heat pump is worth pricing against it before choosing. ENERGY STAR, Boilers covers the certified end of the market. Retrieved 2026-08-23.
- Hot water, and the flue nobody thinks about
- Adding an indirect tank at the same visit takes this job to $12,575 from $10,403. It is the most efficient way to make domestic hot water in a house that already has a boiler, and the piping is open anyway. ⚠️ The related trap runs the other way: if your water heater shares a masonry chimney with the boiler and you fit a condensing boiler, the boiler leaves that flue and the water heater is suddenly alone in a chimney far too large for it. Oversized flues do not draw. That is a liner, and it is the line people find on the invoice rather than the quote.
- Combustion safety, and asbestos
- A boiler is a fuel-burning appliance in a basement, so the four hours of commissioning in the breakdown are a safety check as much as a performance one. CDC, Carbon Monoxide Poisoning Basics and CPSC, Carbon Monoxide Information Center both cover what carbon monoxide means for a household; both retrieved 2026-08-23. ⚠️ And one thing more likely here than on any warm-air job: asbestos pipe insulation. Boiler pipework runs everywhere in a pre-1980s house and the wrapping is a classic place to find it. If it is a grey fabric that has been painted over, do not pull at it — test first. Labour rates from BLS OEWS, May 2025, for plumbers and pipefitters and for electricians, retrieved 2026-08-20, with benefit load from BLS ECEC.
- Material prices
- Modelled estimates, not sourced prices. No public, machine-readable source of US residential material prices exists, and we would rather say so than pretend otherwise. Each line carries its own uncertainty band. How we estimate them.
Contractor overhead and profit applied at 33–43% over direct cost. Data last reviewed 2026-08-23.
What this figure does not include
- Replacing radiators, baseboard or adding underfloor loops
- This prices the boiler and the piping around it, not the emitters. Changing what heats the rooms is a much larger job and is what makes a low-temperature system possible in an old house.
- Oil tanks
- Above-ground or buried, they have their own price, their own lifespan and, if buried, their own environmental liability. None of it is modelled here.
- Electrical service or panel work
- The electric boiler option assumes a suitable feeder already exists, which for a whole-house electric boiler is a strong assumption. When it does not, that is a separate job on our electrical panel page.
- Asbestos on old pipe insulation
- Very common on boiler piping in houses from before the eighties, and much more likely here than on a warm-air system. It is tested rather than disturbed, and abatement is licensed work with its own pricing.
- Buried or inaccessible pipework
- Loops under a slab or behind finished walls cannot be assessed from the inputs this calculator asks for, and replacing them is a different order of job.
- Warm-air heating
- If your house has ducts and vents rather than radiators, you do not have a boiler. That is priced on our furnace page.
Questions people actually ask
How much is a new boiler for a 2000 sq ft house?
About $10,403 in Boston for a standard-efficiency gas hot water boiler with two zones — a 120,000 BTU/h unit, ranging $7,493 to $13,313. A condensing boiler on the same house is $13,198, oil is $12,067 and steam is $10,452. A boiler costs several times what a warm-air furnace of the same output costs, and that is not a markup: it is a pressure vessel full of water with a heat exchanger built to last decades, plus the near-boiler piping that has to be fabricated on site every time.
Is it worth replacing a 20 year old boiler?
A boiler at twenty is not old the way a furnace at twenty is old — cast-iron sectionals routinely run thirty years and more, and the heat exchanger is usually the last thing to fail. The parts that do fail are cheap: circulators, zone valves, controls, the expansion tank. So the honest test is not age. It is whether the block itself is leaking, whether the controls are obsolete enough that parts are getting hard to find, and what you are paying to run it. Replacing a sound twenty-year-old boiler for efficiency alone is a long payback at $10,403, and longer still if your emitters will not let a condensing unit condense.
What is the average lifespan of a boiler system?
We do not publish a lifespan figure because we have no measured source for one, and the ranges quoted elsewhere are too wide to be useful about any individual machine. What is worth saying is that boilers and their systems age differently from warm-air equipment: the boiler itself often outlives two or three sets of circulators and controls, while the pipework and the radiators can be older than everyone in the house and still be fine. That asymmetry is why the useful question is which part has failed, not how many years have passed. A leaking block is a replacement; almost everything else is a repair.
How much does a plumber charge to change a boiler?
On this model 35.5 trade hours go into a straightforward hot-water replacement, priced at the BLS regional wage for plumbers and pipefitters rather than at the HVAC rate — because a boiler is a plumbing job with a burner attached, and in many states it is a different licence. That labour is roughly a third of the $10,403 total here. Getting the old one out is a real part of it: a cast-iron sectional weighs several hundred kilos, sits in a basement with narrow stairs, and is frequently broken into sections where it stands. Steam adds about six hours on top, and a condensing installation about four more for the venting.
Taken from Google’s “people also ask” results for this search on 23 August 2026, not invented.
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The formula, the sources, and an honest account of which parts of the model are weak.