If you’re considering switching from a conventional or system boiler to a combi boiler, one of the first things you’ll want to know is the combi boiler conversion cost.
While combi boilers are popular for their efficiency and space-saving benefits, converting to one is more complex than a like-for-like replacement. In this guide, we’ll explain how much a combi boiler conversion costs, what affects the price, and when a conversion makes financial sense.
In 2026, the cost to convert to a combi boiler typically ranges between £3,000 and £4,500+, depending on the work required.
| Conversion Type | Typical Cost Range |
|---|---|
| System boiler to combi | £3,000 – £4,000 |
| Regular boiler to combi | £3,200 – £4,500+ |
| Conversion with pipework upgrades | £3,800 – £5,000+ |
For a full overview of what’s involved, see our boiler installation service.
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1.Your Existing Heating System
The starting point matters.
System boilers are usually cheaper to convert
Regular boilers often require more work due to tanks and cylinders
Removing these components adds labour time and disposal costs, increasing the combi boiler conversion price.
2.Pipework & Gas Supply
Combi boilers require a strong gas supply. In some properties, a gas pipe upgrade is necessary to meet current regulations and ensure safe operation.
This can significantly affect the combi boiler installation cost.
3.Property Size & Hot Water Demand
Larger homes may need:
Higher-output combi boilers
Additional pipework changes
Careful balancing of hot water demand
This directly impacts how much a combi boiler conversion costs.
| Included Work | Why It Matters |
|---|---|
| Removal of tanks & cylinders | Frees up space and simplifies the system |
| System flushing | Protects the new boiler and improves efficiency |
| Pipework modifications | Ensures correct flow and pressure |
| Boiler commissioning & certification | Required for safety and warranty |
A professional conversion ensures the boiler operates safely and efficiently from day one.
A combi boiler conversion is often worth it if:
You want to remove tanks or cylinders
You need hot water on demand
You’re improving efficiency and space
However, it may not be the best option if:
You have very high simultaneous hot water demand
Water pressure is low
The property is very large
This is why a proper assessment is essential before proceeding with a professional boiler installation or a combi boiler conversion.
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Some homeowners consider conversion only after repeated breakdowns.
| Scenario | Recommended Option |
|---|---|
| Boiler under 8 years old | Repair usually makes sense |
| 10–12+ year old system | Conversion or replacement often cheaper long-term |
| Frequent breakdowns | Conversion strongly recommended |
After conversion, many homeowners also choose boiler cover and home care plans to protect their new system from unexpected repair costs.
You can control costs by:
Choosing the correct boiler size
Avoiding unnecessary system changes
Ensuring proper pipe sizing
Maintaining the system annually
A well-installed combi boiler should last 12–15 years with good care.
The only way to get an accurate combi boiler conversion cost is through a proper survey that considers:
Your current heating system
Property size and layout
Hot water demand
Gas supply
If you’re considering converting, our boiler installation service and Combi Boiler Conversions page provide clear guidance and expert support.
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