Boiler replacement quotes for Ontario homes
A new high-efficiency boiler typically costs $6,000 to $13,000 installed, before HST. Get a free in-home estimate.
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What a boiler replacement costs in Ontario
For a home with radiators or in-floor heat, a new condensing boiler typically costs $6,000 to $13,000 installed, before HST. A combi costs more because it replaces your water heater too.
Combi boiler for heat and hot water (high efficiency)
$7,000 to $13,000
Heating-only hydronic boiler
$6,000 to $11,000
Typical installed prices in Ontario, CAD, before 13% HST. Reviewed October 2026. Estimates, not quotes.
- Install time
- Usually 1 to 2 daysLonger with a flush or new piping
- Busy season
- October to January
- Gas tank water heater
- $1,800 to $3,200What a combi replaces
Typical installed prices in Ontario, CAD, before 13% HST, for a standard replacement in an existing detached home. Reviewed October 2026. Estimates, not quotes. Ranges are for hot water systems; steam is quoted case by case. Forced-air furnace and heat pump ranges are on the FurnaceQuotes home page.
Combi boiler or a boiler with an indirect tank?
Pick a combi for a smaller home with one or two bathrooms. Pick a heat-only boiler with an indirect tank when several showers run at once.
Combi boiler
- Heat plus hot water on demand
- No tank, so it frees floor space
- Limited flow: two showers at once can run lukewarm
Heat-only boiler and indirect tank
- The boiler also heats a separate insulated tank
- Stored hot water serves several taps at once
- Needs room for the tank and costs more
- Heat-only boiler
- $6,000 to $11,000
- +New gas tank water heater
- $1,800 to $3,200
- =Two appliances
- $7,800 to $14,200
One combi boiler$7,000 to $13,000
A combi makes the most sense when the old tank is near the end of its life. If it is new, or rented with years left on the contract, check the terms and any removal charges first.
What a boiler quote should include
A good hydronic quote is a plan for your whole heating system, not just a boiler swap. Each of these lines belongs on it, in writing.
| Line item | What it should say | Why it matters |
|---|---|---|
| Sizing | A heat loss calculation, not the old boiler's label | Old cast-iron boilers are often oversized |
| Boiler | Model number, AFUE, output and turndown | A wide turndown runs low and steady on mild days |
| Venting | Material, route and exit point | Condensing boilers cannot use an old chimney as is |
| Condensate | A neutraliser and the drain route | Condensate is acidic |
| Piping | Near-boiler loops or a hydraulic separator, air and dirt separators | Protects the narrow heat exchanger |
| Pumps and tank | Variable-speed circulators, expansion tank, fill and relief valves | Worn parts cause pressure problems later |
| System flush | Clean, flush and water treatment | Sludge can clog a new boiler and risk its warranty |
| Controls | Outdoor reset, thermostats, zone valves or pumps | Lower water temperatures let the boiler condense |
| Permits and removal | Who applies, TSSA-registered gas work, old boiler haul-away | Cast iron is heavy; removal is real labour |
Why a heat loss calculation mattersQuestions to ask before signingCompare boiler quotes side by side
Want a quote that covers the whole system, not just the boiler?
Get A Free QuoteRisks to raise before you sign
Most problems after a boiler install trace back to the old system. Ask about these at the estimate so they are priced now, not found on install day.
Sludge in old cast iron
Rust and sediment settle in radiators and pipes. Ask for a flush and a dirt separator.
An orphaned water heater
If the boiler and a gas water heater shared a chimney and the new boiler vents out the wall, the heater is left alone in a flue sized for two. It can draft poorly, so ask about a chimney liner.
Water temperature
Condensing boilers are most efficient when return water is below about 54°C (130°F). Ask how the outdoor reset will be set.
Old pipe insulation
White or grey wrap on older pipes can contain asbestos. Have it tested before anyone cuts pipes.
Tired valves
Old radiator and zone valves often leak once a system is drained and refilled. Ask what a fix costs.
Radiators plus in-floor
They need different water temperatures, so the quote should show a mixing valve or separate zone.
- Venting changes or a chimney liner
- $300 to $1,500
- Gas piping
- $300 to $1,200
Typical add-on prices in Ontario, before HST. Reviewed October 2026. Only some homes need each item.
A chimney liner falls under venting. Gas line work comes up most when an oil boiler is converted to natural gas.
How long a boiler replacement takes
Plan on one to two days. A like-for-like swap can finish in one; a flush, new near-boiler piping or a venting change adds time.
Estimate visit
Boiler, radiators or floor loops, venting, gas line and water heater checked, and the home measured for heat loss.
Written quote
Model numbers and the piping and venting plan. No pressure to sign.
Drain and remove
System drained, old boiler disconnected and carried out.
Set, pipe and vent
New boiler, piping, pumps and venting installed, then the system is flushed, refilled and purged of air.
Start-up
Combustion checked, outdoor reset and zones set, then a walkthrough.
Gas safety and rebates
Ask for the TSSA registration number. If a rebate comes up in a boiler quote, check it on the official pages before you count on it.
Gas work in Ontario
In Ontario, only a TSSA-registered contractor, using certified gas technicians, may install or repair gas appliances. Ask for the company's TSSA registration number and the technician's certificate before work starts. We do not certify, license or inspect any company.
Rebates: check before you sign
Ontario's Home Renovation Savings program offers heat pump rebates with eligibility rules by heating fuel, home type and product, and it requires approval before installation. Program rules change often, so check the official pages before you buy and never sign because of a promised rebate amount. New applications for the Canada Greener Homes Loan ended on October 1, 2025.
Common questions
Straight answers. If yours is not here, the company can answer it during your free estimate.
How much does a boiler replacement cost in Ontario?
A high-efficiency heating boiler typically costs $6,000 to $11,000 installed, and a combi boiler that also makes your hot water $7,000 to $13,000, before HST. A system flush, near-boiler piping, venting changes and zone controls move the price most. Your written quote after an in-home visit is the real number.
Is a combi boiler a good idea for my home?
A combi suits smaller homes with one or two bathrooms, where hot water runs at one or two taps at a time. It saves space and replaces the tank. In larger homes, or where showers overlap, a heat-only boiler with an indirect tank usually gives better hot water.
Could I swap my boiler for a forced-air furnace?
You can, but it means running new ductwork through finished walls and ceilings, which adds a lot of cost and mess. Most radiator homes keep hot water heat and replace the boiler. For cooling, ductless mini-splits are a common add-on that needs no ducts.
Do old radiators work with a new condensing boiler?
Yes. Cast-iron radiators work well with condensing boilers, especially with an outdoor reset control lowering the water temperature on milder days. Many older radiator systems were sized for draftier houses, which lets the boiler run cooler and condense more. A flush first protects the new heat exchanger.
Who can install a boiler in Ontario?
Gas boilers must be installed by a TSSA-registered contractor using certified gas technicians. Building permit rules for boiler replacements vary by municipality. The quote should say who applies for any permit and whether the fee is included. Ask for the registration number before work starts.
Get a boiler quote that covers the whole system
Answer a few quick questions. A participating local HVAC company confirms the details, checks your system and quotes the boiler, piping and venting in writing.
Takes under a minute. No cost, no commitment.