Boiler replacement typically costs somewhere around $3,600 to $9,000 installed, and the national averages that cost guides report land close to $6,000. Gas and oil boilers commonly fall in the $4,000 to $9,000 range, while condensing boilers, steam boilers and jobs with venting, gas line or piping changes push the total higher. Fuel type, boiler type, the size your house actually needs and the condition of the boiler room drive most of the difference.
The good news with hydronic heat is that your radiators, baseboard and piping usually outlast several boilers, so a replacement is normally the boiler and its near-boiler parts, not the whole system. If you're still deciding whether your current boiler can be saved, see boiler repair and when to replace.
New Boiler Cost by Fuel and Type
| Boiler | Typical installed range in cost guides | Notes |
|---|---|---|
| Natural gas, hot water | About $4,000 to $9,000 | The most common replacement |
| Oil | About $4,800 to $9,000 | Tank, chimney and burner work can add more |
| Electric | About $1,800 to $8,000 | Lower equipment cost, but may need an electrical service upgrade and costs more to run |
| Condensing gas (90%+ AFUE) | Upper end of the gas range and above | Needs plastic venting and a condensate drain |
| Combi (heat and hot water) | Varies widely between sources | Replaces a separate water heater too |
| Steam | Often higher than hot water | Specialized near-boiler piping; can't be condensing |
These are typical ranges collected from national cost guides, not quotes. Where sources disagreed widely, as they do on combi boilers, we haven't listed a number. Labor alone commonly runs about $1,000 to $3,000 of the total, depending on how much piping the installer has to change.
Equipment vs. installed price
A boiler's equipment price is only part of the bill. The installed price adds removing the old boiler, near-boiler piping, venting, controls, the expansion tank and valves that often get replaced at the same time, permits, startup and haul-away. On a straightforward swap, the boiler itself is often less than half the invoice.
Steam boiler replacement cost
Steam boilers often cost more than hot water boilers to replace, though the cost guides do not agree on a number. The reasons are specific to steam:
- Near-boiler piping. The risers, header and equalizer have to follow the manufacturer's piping diagram.
- Skimming and cleaning. A new steam boiler is usually skimmed and cleaned after startup.
- No condensing option. Steam boilers cannot be condensing.
- Different sizing. A steam boiler is sized to the connected radiation (the total EDR of the radiators), not just the heat loss, so the installer should measure the radiators.
Ask the installer about steam experience, and whether replacing the near-boiler piping is in the quote.
What Drives Boiler Replacement Cost
| Factor | Pushes cost up | Keeps cost down |
|---|---|---|
| Fuel | Oil, or switching fuels | Staying on the same fuel |
| Efficiency | Condensing boiler with new venting | Non-condensing replacement in the same vent |
| Type | Steam, or combi replacing a water heater | Heat-only hot water boiler |
| Size | Larger output for a big or leaky house | Right-sized by heat loss calculation |
| Venting | New PVC vent, chimney liner for an orphaned water heater | Existing vent reused safely |
| Piping | Primary/secondary loops, new circulators, zone changes | Near-boiler piping reused |
| Water quality | System flush, dirt separator, water treatment | Clean system with good water |
| Domestic hot water | Adding an indirect tank | Keeping the existing water heater |
| Access | Tight basement stairs, crawlspace boiler room | Open, easy-access boiler room |
| Permits and code | Gas line upsizing, combustion air, electrical | Existing setup already meets code |
Hidden Costs Most Boiler Quotes Gloss Over
Several items rarely show up in national averages but change real quotes a lot.
Venting changes. A condensing boiler vents through plastic pipe, often out a sidewall, instead of the chimney. If a gas water heater shared that chimney, it's now alone in a flue that may be too big for it. That can cause poor draft and backdrafting, which brings carbon monoxide risk. The fix is usually a properly sized chimney liner or a different water heater, and it should be in the quote.
Getting the most from a condensing boiler. A condensing boiler only reaches its rated efficiency when return water comes back cool enough to condense the flue gas, which is generally below about 130 degrees. Systems with cast iron radiators sized for very hot water may not get there often. Outdoor reset controls, which lower water temperature in milder weather, help close that gap. Our boiler vs furnace comparison explains the issue in more detail.
System flush and water treatment. Old hydronic systems carry sludge and magnetite. Modern compact heat exchangers, especially in condensing boilers, are less tolerant of that debris. Many manufacturers call for a system flush, and installers often add a dirt or magnetic separator. Ask whether yours does and whether the quote includes it.
Near-boiler piping. Many modern boilers need primary/secondary piping or a hydraulic separator so the boiler gets the flow it needs regardless of how many zones are calling. That's piping and pump work beyond simply connecting the old pipes.
Steam systems. Steam boilers need specific near-boiler piping set by the manufacturer, and they can't be replaced with a condensing boiler. A steam boiler should be sized from the connected radiation (a radiator survey), not from the old boiler's nameplate.
Domestic hot water. If you add an indirect water heater fed by the boiler, or switch to a combi boiler that makes hot water on demand, that changes both cost and how the system should be sized.
Sizing: Don't Just Copy the Old Boiler
Many older boilers are oversized. Houses get new windows and insulation over the decades, and original installers often sized generously. An oversized boiler short-cycles, wears faster and wastes fuel. For hot water systems, ask for a room-by-room heat loss calculation. For steam, the installer should measure your radiators to calculate the connected load. A smaller, right-sized boiler can cost less to buy and run.
Repair or Replace Your Boiler?
Boilers commonly last 15 to 30 years, with cast iron at the long end. Replacement usually makes sense when:
- The boiler is past about 15 to 20 years and needs a major repair
- The heat exchanger or a cast iron section is cracked or leaking
- The repair costs more than half the price of a new boiler
- Repairs are becoming a yearly event
- Fuel bills keep rising, or the boiler is a low-efficiency model in a long heating season
Pumps, zone valves, expansion tanks, relief valves and ignition parts are normal wear items and usually worth repairing on a boiler that's mid-life. For lifespan by system type, see how long furnaces and boilers last.
How to Compare Boiler Replacement Quotes
Ask each installer to put these in writing:
- Make, model and output of the boiler, and how the size was calculated
- AFUE rating and whether it's condensing
- Venting plan, including what happens to any water heater on the same chimney
- Piping scope: primary/secondary or a hydraulic separator, circulators, zone valves
- System flush and water treatment, and any dirt separator
- Controls: outdoor reset, thermostat changes, low-water cutoff
- Parts replaced with it: expansion tank, relief valve, fill valve, backflow preventer
- Permit, combustion test and startup procedure
- Warranty terms, heat exchanger and parts coverage, labor coverage and registration deadline
- Removal and disposal of the old boiler and any oil tank work
Hire a contractor experienced with hydronic heat, and with steam if that's what you have. Gas, venting and combustion work isn't a DIY job: a mistake can cause a carbon monoxide leak or a fire, and most jurisdictions require a licensed installer and a permit.
Ways to Lower Your New Boiler Cost
- Replace before it fails. Planning in summer gives you time to compare quotes; a midwinter failure doesn't.
- Right-size it. A heat loss calculation can justify a smaller boiler.
- Keep the scope honest. Pay for the flush, venting fix and controls that matter, but question extras you didn't ask for.
- Compare systems once. For a wider view, our guide to HVAC replacement cost across every system shows how a boiler compares with a furnace or heat pump.
- Look at incentives. Federal tax credit rules changed in 2025, so check current federal, state and utility rebates before you count on one.
If you're weighing efficiency tiers, our page on AFUE and high efficiency heating explained covers how to estimate fuel savings between an older unit and a high-efficiency one. The same AFUE math applies to boilers.
Frequently Asked Questions
How much does it cost to replace a boiler?
Most national cost guides report an average boiler replacement cost close to $6,000, with typical jobs falling somewhere around $3,600 to $9,000 installed. Condensing boilers, oil systems, steam boilers and jobs that need new venting, gas lines or major piping changes can cost more.
How long does boiler replacement take?
A like-for-like hot water boiler swap often takes one to two days. Converting to a condensing boiler, adding an indirect water heater, changing fuel or repiping the boiler room can stretch the job to several days.
Is it worth replacing an old boiler?
Usually, if it's past 15 to 20 years old and needs a major repair, or if it's a low-efficiency unit and you have a long heating season. ENERGY STAR suggests considering replacement for furnaces and boilers more than 15 years old. A cracked heat exchanger or a leaking cast iron section is normally a replacement.
What size boiler do I need?
Size should come from a room-by-room heat loss calculation for hot water systems, or a radiator survey for steam systems. Copying the old boiler's rating often oversizes the new one, since many older boilers were sized generously and the house may have been insulated since.
Can I replace a boiler with a furnace?
You can, but it usually costs far more than a new boiler because you'd need ductwork throughout the house. Most homeowners with working radiators or baseboard replace the boiler with another boiler, or add a heat pump alongside it.
How much does a new boiler furnace cost?
A boiler furnace usually means a boiler, which heats water or steam for radiators or baseboard. A typical installed boiler replacement lands around $3,600 to $9,000, with gas and oil commonly $4,000 to $9,000. If your system blows warm air through ducts, it is a furnace, and the furnace replacement cost guide applies.