AFUE depends on fuel: natural gas and propane 90% or 95%, oil 86% or 87%. Electric boilers run at about 99% and ignore this choice.
💰 Total Installed Cost
✅ AFUE Efficiency
Cost Breakdown
Full Cost Table
| Item | Basis | Cost |
|---|
How to Use the Boiler Replacement Cost Calculator
Choose the fuel source, since it affects both equipment pricing and any venting or fuel supply work needed.
Choose the boiler output in BTU/hr that matches the home's heating load, ideally confirmed by a proper heat loss calculation.
Choose the code minimum or high-efficiency tier to see the cost and AFUE tradeoff. Electric boilers ignore this choice.
Click Calculate Installed Cost to see equipment cost, labour cost, and total installed cost.
What Drives Boiler Replacement Cost
Boiler replacement cost comes down to three main factors: fuel type, output size, and efficiency tier. Unlike a furnace swap, a boiler replacement often interacts with an existing hydronic distribution system, whether that's cast iron radiators, baseboard, or in-floor radiant loops, which mostly stay in place during a like-for-like replacement.
Why Gas Boilers Now Need New Venting
A condensing boiler pulls extra heat out of the flue gases using a secondary heat exchanger, which cools the exhaust enough that the old metal chimney is no longer suitable. That means new sidewall or vertical PVC, CPVC, or polypropylene venting and a condensate drain, both of which add labour and material cost beyond the boiler itself. This now applies to nearly every gas replacement, because household gas boilers for hot water systems made since July 1, 2023 must reach at least 90 percent AFUE under Canada's Energy Efficiency Regulations. The code minimum tier here therefore carries $900 of venting work for natural gas and propane, and the high-efficiency tier steps up from 90 to 95 percent AFUE for a 20 percent equipment premium, or about $1,100 on a 120,000 BTU/hr unit.
Fuel Type Changes More Than Just the Burner
Natural gas boilers are usually the most straightforward and least expensive to install where gas service already reaches the home, since the fuel line is already in place. Oil systems often trigger a tank inspection, and an aging tank may need replacement as part of the project; oil boilers also stay non-condensing, with the federal minimum for household oil-fired hot water boilers set at 86 percent AFUE, so they keep an existing chimney more often. Propane systems can require a new or relocated tank. Electric boilers skip venting and fuel line work entirely, trading that simplicity for a generally higher cost per unit of heat delivered given typical electricity rates. At 120,000 BTU/hr and code minimum efficiency, this calculator returns $8,500 for natural gas, $9,675 for propane, $9,575 for oil, and $6,775 for electric.
What Stays in Place and What Gets Replaced
In most replacements the radiators, baseboard, or in-floor loops stay and connect to the new boiler. Two things deserve a look first. A condensing boiler only condenses when return water is below roughly 55 °C (130 °F), so older radiators sized for hot supply water can limit the efficiency gain unless the system runs at lower temperatures. The expansion tank is the other, since the old one may be waterlogged or too small for the new system's water volume, and the expansion tank calculator shows what size to expect.
Confirm Sizing Before Pricing
An oversized boiler short-cycles, wearing out components faster and rarely running long enough to reach peak efficiency, while an undersized one struggles to keep up on the coldest days. If the home's heating load hasn't been properly confirmed, run it through the boiler sizing calculator before locking in an output size here.
Comparing Against a Furnace or Heat Pump
Not every home needing a heating system replacement is locked into hydronic distribution. If the home is on forced air, compare this against the furnace cost calculator or heat pump cost calculator to see how the options stack up.
Frequently Asked Questions
Based on this calculator's pricing, a natural gas boiler at the 90 percent AFUE code minimum runs about $7,700 to $10,400 installed depending on output size, and the 95 percent high-efficiency tier runs about $8,700 to $11,800. A 120,000 BTU/hr natural gas boiler at code minimum comes to $8,500. Propane and oil systems cost more, and the highest result in this tool is about $13,500 for a 199,000 BTU/hr propane boiler at the high-efficiency tier. Get a written quote before committing.
A condensing boiler extracts additional heat from the flue gases with a secondary heat exchanger, which cools the exhaust too much for a traditional metal chimney. It needs sidewall or vertical PVC, CPVC, or polypropylene venting plus a condensate drain, and those parts add to both equipment and labour cost. Since July 1, 2023, new household gas boilers for hot water systems sold in Canada must reach at least 90 percent AFUE, so this calculator adds $900 of venting labour to every natural gas and propane boiler. Oil boilers are not condensing and can often keep their chimney.
Yes. For a 120,000 BTU/hr boiler at code minimum, this calculator gives $8,500 on natural gas, $9,675 on propane, $9,575 on oil, and $6,775 on electric. Natural gas is usually the least expensive where gas service already exists, since the fuel line is in place. Oil systems often need tank inspection or replacement, and propane systems may need a new or relocated tank, which is why those fuels carry extra labour here. Electric boilers avoid venting and fuel line work entirely, but they usually cost more to run than gas given electricity rates relative to heating output.
In most straightforward replacements, existing radiators, baseboard, or in-floor radiant loops stay in place and connect to the new boiler, which keeps costs closer to a like-for-like swap. One caution is that a condensing boiler only condenses when return water is below roughly 55 °C (130 °F), so older radiators built for hot supply water can limit the efficiency gain. If the distribution system itself needs work, such as replacing old cast iron radiators or adding zones, that is a separate cost beyond the boiler replacement itself.
Related HVAC Tools
Forced-air alternative
Heating and cooling combined
Full year energy cost
Full system replacement
Monthly payment estimate
Available government rebates