Combi boiler
A combi boiler provides heating and hot water without a separate hot water cylinder. It is a common option for many UK homes, especially where space is limited or hot water demand is moderate.
Boiler installation cost calculator
Boiler Installation Cost Calculator UK
Estimate the cost of installing or replacing a boiler in a UK home based on boiler type, property size, installation complexity, controls, location, access and region. Use this calculator for gas boiler replacement, combi boiler installation, system boiler upgrades and regular boiler replacement planning.
Boiler installation or boiler replacement?
The cost changes depending on whether the job is a straightforward replacement, a boiler relocation, a system conversion or a new installation. The more the pipework, flue route, condensate drainage and hot water setup change, the wider the estimate becomes.
| Situation | Better description | Why it matters |
|---|---|---|
| Existing boiler replaced in the same place | Boiler replacement | This is usually simpler because the main pipework, location and flue route may already be suitable. |
| Boiler moved to another room | Boiler installation with relocation | Pipework, flue routing, condensate drainage, controls and making good may change. |
| Old cylinder system changed to combi | Boiler conversion | Cylinder removal, hot water changes and pipework alterations can increase the project scope. |
| No existing central heating boiler | New boiler installation | More work may be needed around pipework, controls and heating system setup. |
| Comparing with low-carbon heating | Heating system comparison | Use the Heat Pump Cost Calculator as well if you are comparing heating options. |
Which boiler type are you pricing?
Boiler type affects the estimate because combi, system and regular boilers use different hot water arrangements and may need different levels of installation work.
System boiler
A system boiler works with a hot water cylinder and may suit homes with higher hot water demand. Installation costs can change if the cylinder, controls or existing pipework need upgrading.
Regular / heat-only boiler
A regular boiler is often found in older heating systems with a cylinder and cold water storage. Replacement can be more complex if the wider system is dated or being altered.
Typical UK boiler installation cost ranges
These are broad planning ranges. Use the calculator above for a more specific estimate based on boiler type, property size, system condition, access, region and contingency.
| Boiler project | Typical planning range | Best use |
|---|---|---|
| Like-for-like combi boiler replacement | £2,000–£4,000+ | Existing combi, same location |
| Combi boiler conversion | £3,000–£6,000+ | Moving from a cylinder system to combi |
| System boiler replacement | £2,500–£5,000+ | Homes with a hot water cylinder |
| Regular boiler replacement | £2,800–£5,500+ | Older systems or larger homes |
| New boiler installation with extra work | £4,000–£7,500+ | More pipework, controls or location changes |
A survey is needed before an installer can confirm a fixed price.
What affects boiler installation cost?
The boiler itself is only one part of the estimate. The final cost can change because of the existing system, flue route, condensate drainage, controls, access and whether the project is a replacement or a conversion.
Boiler type
Combi, system and regular boilers have different installation requirements, hot water arrangements and cost bands.
Like-for-like or conversion
A same-location replacement is usually simpler than relocating the boiler or converting from a cylinder system to a combi setup.
Property size
Larger homes may need a higher-output boiler, larger hot water setup or more system balancing after installation.
Flue and condensate route
The flue position and condensate drainage can add labour if they are awkward, non-compliant, blocked or need changing.
Existing pipework and radiators
Older systems may need flushing, valves, pipework changes or radiator checks before the new boiler can perform properly.
Controls and specification
Smart controls, thermostats, radiator valves, premium boilers and longer warranties can raise the estimate.
Boiler or heat pump?
A boiler replacement is often the starting point when the existing gas heating system is staying in place. A heat pump is a different type of heating project because it may depend on radiator sizing, hot water storage, insulation and lower flow temperatures.
| Question | Boiler calculator | Heat pump calculator |
|---|---|---|
| Replacing an existing gas boiler? | Best starting point | Useful for comparison |
| Moving away from gas heating? | Less relevant | Best starting point |
| Existing insulation is poor? | Estimate may still help | Check insulation costs first |
| Radiators may need upgrading? | Sometimes relevant | Often important |
| EPC improvement is the goal? | One possible upgrade | One possible upgrade |
Boiler installation and EPC improvement planning
A boiler upgrade may help improve heating efficiency, but EPC improvement is usually wider than one appliance. Insulation, heating controls, solar panels and heat-loss reduction can all affect the result. If your main goal is improving the property’s rating, use the EPC Improvement Cost Calculator and compare it with the Insulation Cost Calculator and Solar Panel Cost Calculator.
What may be included in a boiler installation estimate?
A boiler quote can include different items depending on installer, specification and property condition. Use this table to understand what may sit inside or outside a typical estimate.
| May be included | May be excluded |
|---|---|
| Boiler appliance | Major radiator replacement |
| Standard labour | Full central heating installation |
| Flue kit | Structural alterations |
| Basic controls | Extensive pipework replacement |
| Condensate connection | Electrical upgrades outside normal scope |
| Commissioning | Asbestos removal or specialist remedial work |
| Waste removal | Decorative making good |
When a boiler installer needs to inspect the property
A survey is needed before a fixed quote because the installer has to check the existing boiler position, gas supply, flue route, condensate drainage, pipework, radiators, controls, hot water setup, access and safety requirements.
Gas supply and output
The installer needs to confirm whether the gas supply and boiler output are suitable for the property and hot water demand.
Flue route
The flue position must be suitable for the property layout, access and installation requirements.
Condensate drainage
Condensate routing can affect labour if drainage access is awkward or needs alteration.
Pipework and radiators
Older pipework, radiator valves or system sludge can affect installation scope and long-term performance.
Hot water setup
Cylinder condition, removal, replacement or conversion work can change the cost range.
Access and working space
Lofts, cupboards, flats, parking restrictions or tight working areas can increase labour time.
How this boiler installation estimate is calculated
The calculator starts with a base cost range for the selected boiler type, then adjusts the estimate using project type, property size, existing system condition, flue and condensate complexity, cylinder work, controls, access, specification level, region and contingency.
This approach is designed for early planning. A fixed quote can change after an installer checks the boiler location, flue route, condensate drainage, gas supply, heating controls, pipework, radiators and hot water setup.
For more detail, read our methodology, pricing data and how costs are calculated.
Boiler installation cost FAQs
How much does boiler installation cost in the UK?
Boiler installation in the UK can range from a few thousand pounds for a straightforward replacement to a higher amount for conversions, relocation, cylinder work, difficult access or wider heating system upgrades. Use the calculator for a project-specific planning range.
What affects the cost of a new boiler?
The main cost drivers are boiler type, project type, property size, existing system condition, flue route, condensate drainage, cylinder work, controls, access, specification level and region.
Is a combi boiler cheaper than a system boiler?
A combi boiler can be cheaper in some replacement projects because it does not need a separate hot water cylinder. A system boiler may cost more if cylinder work, controls or hot water upgrades are needed.
Does moving a boiler increase the cost?
Yes. Moving a boiler can increase cost because pipework, flue routing, condensate drainage, electrical connections, access and making good may all change.
Is this calculator for boiler repair?
No. This calculator is for boiler installation and replacement. It is not designed for servicing, minor repairs or emergency boiler callout costs.
Should I compare a boiler with a heat pump?
Yes, if you are considering a low-carbon heating option or moving away from gas heating. Use the Heat Pump Cost Calculator to compare the wider installation scope.
Can a new boiler improve an EPC rating?
A more efficient boiler may help, but EPC improvement often depends on the whole property. Insulation, heating controls and solar panels may also matter, so use the EPC Improvement Cost Calculator for wider planning.
Are CostIntel boiler estimates fixed quotes?
No. The estimates are planning ranges based on typical UK boiler installation cost drivers. An installer needs to inspect the property before giving a fixed quote.