A boiler replacement is not a commodity service. Two homes on the same street can receive quotes that differ by $3,000 or more, and both quotes can be entirely accurate for what each specific home requires. Existing gas line capacity, venting configuration, the type of hydronic distribution system, and whether a combi or dedicated boiler is being installed all affect the final number.
The most common reason for sticker shock is a quote that omits infrastructure work until installation day. A licensed plumber should assess the gas supply line, existing venting, and the hydronic distribution system before producing a final price. Our boiler and combi boiler services team (/boiler-combi-boiler-services) includes this assessment as part of the quoting process so nothing surfaces unexpectedly once work begins.
A standard high-efficiency hot water boiler replacing an existing unit of the same type, with compatible venting and an existing gas supply line of appropriate capacity, typically costs between $4,000 and $7,000 installed in the GTA. This range assumes a like-for-like replacement where minimal infrastructure changes are required.
The equipment alone for a residential hot water boiler ranges from $1,500 to $4,000 depending on the brand, output capacity in BTUs, and efficiency rating. High-efficiency condensing models at 90% AFUE or higher command a premium over standard efficiency models but reduce annual operating costs meaningfully.
A combi boiler installation that replaces both a boiler and a separate water heater typically costs between $5,500 and $9,500 installed, depending on the unit capacity, required venting changes, and whether the domestic hot water demand of the household is well-matched to the combi unit's flow rate. Higher-capacity condensing combi models at the upper end of the residential range can push above that.
The equipment cost for a residential combi boiler ranges from $2,500 to $5,000. The additional cost compared to a dedicated boiler reflects the integrated domestic hot water function and the higher-efficiency heat exchanger required to handle both loads. Our combi boiler services page (/boiler-combi-boiler-services) explains when a combi unit makes sense versus maintaining separate systems.
Cast iron sectional boilers, common in older GTA homes built before the 1980s, are typically replaced with modern high-efficiency equivalents rather than like-for-like cast iron systems. The installed cost for this type of replacement generally falls between $5,000 and $10,000 because it often involves updating the venting system, resizing the gas supply line, and in some cases adjusting the distribution system to accommodate a modern boiler's lower operating water temperature.
The boiler unit itself typically represents 40% to 55% of the total installed cost. Within that range, efficiency rating is the primary variable. A standard efficiency boiler at 80% AFUE costs less upfront than a condensing model at 95% AFUE, but the operating cost difference accumulates meaningfully over the system's lifespan. In Ontario's climate, where heating season runs roughly 6 months, that efficiency gap produces real annual savings.
All gas line work in Ontario must be performed by a TSSA-licensed gas technician. If the existing gas supply line is undersized for the new boiler's BTU input requirements, upgrading it adds cost depending on the pipe diameter change required and the length of the run. This is a non-negotiable safety and performance requirement, not an upsell.
High-efficiency condensing boilers require PVC or CPVC venting rather than the metal flue used on standard efficiency models. If the replacement involves switching from a standard to a high-efficiency unit, the existing metal flue cannot be reused. New venting materials, routing, and exterior penetrations add to the installed total. The specific cost depends on the venting run length and whether the exterior penetration location is straightforward or requires routing through finished walls.
Boiler replacement in Ontario requires a permit and inspection in most municipalities. Permit fees for gas-fired heating equipment typically fall between $100 and $300 depending on the municipality. A licensed plumber should pull the permit as part of the project. An offer to skip the permit to reduce the quote is a red flag that creates liability for the homeowner and can affect insurance coverage if an incident occurs.
If the existing hydronic distribution system requires balancing, zone valve replacement, or circulator pump work as part of the boiler replacement, that adds to the installed cost. A new boiler installed on an unbalanced or poorly maintained distribution system will not perform at its rated efficiency. Our team assesses the full hydronic system as part of the replacement process, not just the boiler itself.
High-efficiency condensing boilers that meet ENERGY STAR certification requirements may qualify for rebates through the Canada Greener Homes program or through Enbridge Gas efficiency incentive programs. These programs change in structure and eligibility regularly. A licensed plumber can confirm which specific models qualify at the time of the quote and can advise on the application process.
In some cases, a rebate on a high-efficiency condensing boiler narrows the cost gap between a standard efficiency replacement and a premium unit substantially, changing the payback calculation significantly. Contact our team (/contact) to ask about currently eligible models before committing to equipment selection.
A boiler that fails completely in mid-winter eliminates your ability to plan, compare quotes, or schedule at standard rates. Emergency boiler replacements in the GTA often involve after-hours labour rates, expedited parts sourcing, and compressed timelines that limit your ability to evaluate options. The total cost difference between a planned replacement and an emergency replacement can be significant.
If your boiler is over 15 years old or showing the warning signs described in our guide on when to replace your boiler (/blog/when-to-replace-boiler), a proactive replacement before failure is almost always the less expensive and less stressful path. Galaxy Plumbing responds to emergency boiler failures across the GTA when planning is not possible. Our emergency HVAC team (/emergency-plumbing-hvac-services) is available around the clock.
Galaxy Plumbing provides itemized boiler replacement quotes across Toronto, Mississauga, Scarborough, Oakville, and Etobicoke. Our licensed team assesses the gas supply line, existing venting, and hydronic distribution system before producing a price, so the quote you receive reflects what your home actually requires. Contact our team (/contact) to book an assessment and get transparent pricing for both repair and replacement options before you commit.
A straightforward boiler replacement on an existing compatible system typically takes one full working day, roughly 6 to 8 hours including removal of the old unit, installation of the new boiler, venting connection, gas line hookup, and system testing. Replacements requiring significant venting changes, gas line upgrades, or hydronic system work may extend to two days. Emergency replacements under time pressure may be completed more quickly where the existing infrastructure is compatible.
In most cases, yes. Existing radiators and baseboard convectors are compatible with modern high-efficiency boilers, though the boiler's operating water temperature may need to be adjusted to suit the distribution system. High-efficiency condensing boilers operate most efficiently at lower water temperatures, which works well with properly sized radiator systems. A licensed plumber should assess the existing distribution system as part of the replacement process.
A boiler heats water and distributes it through radiators, baseboard convectors, or in-floor heating systems. A furnace heats air and distributes it through ductwork. They are fundamentally different systems that cannot be used interchangeably without major infrastructure changes. If your home has radiators or in-floor heating, you have a boiler-based hydronic system. If your home has forced-air vents, you have a furnace-based system.
If both systems are approaching end of life, replacing them at the same time can reduce total labour cost and may be an opportunity to consolidate into a combi boiler that handles both functions. If only the boiler needs replacement and the water heater has meaningful remaining life, replacing both is not necessary. A licensed plumber can assess both systems and give you an honest recommendation based on the age and condition of each.
Replacing an aging boiler with a new licensed and permitted installation generally improves your home's mechanical systems profile, which insurers view positively. An unpermitted installation or a failed inspection creates liability risk that can affect coverage. Always ensure the replacement is performed by a licensed plumber who pulls the required permit and completes the inspection process.
