A combi boiler is the most popular choice for UK homes — and for good reason. No water tank, no cylinder, hot water on demand. But before you commit, two questions usually come first: how much will it cost and how long will my home be without heating?
Here are the honest answers.
What Does a Combi Boiler Installation Cost in 2026?
The total cost of a combi boiler installation — supply and fit — typically falls between £1,800 and £3,500.
What determines where your quote lands:
At Boilers On-Demand, combi installations in Sussex and Surrey start from £1,699, with most jobs sitting around £2,800.
What Affects the Cost of a Combi Boiler Installation?
Boiler Brand and Warranty Differences
The boiler itself — entry-level models cost less upfront but often carry shorter warranties. Mid-range brands like Vaillant and Baxi offer the best balance of efficiency, reliability, and manufacturer guarantee — up to 12 years with approved installers.
Like-for-Like Combi Boiler Swaps
Replacing an existing combi in the same position is straightforward.
Converting from a System or Regular Boiler
Converting from a regular or system boiler to a combi involves removing the tank, cylinder, and additional pipework. That adds cost and time.
Pipework and Flue Requirements
Your property — older homes can present additional flue requirements or pipework complications. A proper survey identifies these before any work begins, so there are no surprises on the day.
How Long Does a Combi Boiler Installation Take?
Typical Installation Timelines Explained
For a straight swap — same boiler type, same location — most installations are completed in a single day.
| Installation Type | Typical Time |
|---|---|
| Like-for-like combi swap | 4–6 hours |
| Combi swap with minor pipework adjustments | 6–8 hours |
| Full system conversion (removing tank and cylinder) | 1–2 days |
Same-Day Boiler Installation Options
Our engineers arrive at the agreed time, work cleanly, and won't leave until your new system is fully commissioned and you're comfortable with how it operates.
What's Included in a Combi Boiler Installation Quote?
A fair, full quote should always include:
Gas Safe Certification and Handover
- Supply of the new boiler
- Removal and responsible disposal of the old one
- Full installation and commissioning
- Gas safety check and certification
- Handover — walking you through the controls
- Manufacturer guarantee registration
If a quote doesn't itemise these, ask why.
Is a Combi Boiler Right for Your Home?
Combi boilers are ideal for smaller and mid-sized homes with one or two bathrooms and moderate hot water demand. They're compact, efficient, and widely supported by all major manufacturers.
If you have three or more bathrooms, or multiple people regularly using hot water simultaneously, a system boiler may serve you better. A free survey will tell you which suits your home — without pressure either way.
Frequently Asked Questions
- How much does a combi boiler installation cost in 2026?
- A combi boiler installation typically costs between £1,800 and £3,500 including supply and installation depending on the boiler brand and complexity of the work.
- How long does a combi boiler installation take?
- A like-for-like combi boiler swap is usually completed within 4–6 hours, while full system conversions can take between one and two days.
- What is included in a combi boiler installation?
- Installation typically includes the new boiler, removal of the old boiler, full installation, commissioning, gas safety checks, certification and manufacturer guarantee registration.
- Is a combi boiler suitable for every home?
- Combi boilers are ideal for smaller and mid-sized homes with moderate hot water demand. Larger homes with multiple bathrooms may benefit more from a system boiler.
- Do you offer finance for combi boiler installations?
- Yes. Flexible finance options are available to spread the cost of a new combi boiler installation.
Get a Same-Day or Next-Day Boiler Quote
Gas Safe registered. 36+ years of local experience. Up to 12-year guarantee on every installation.
If you're ready to find out exactly what a combi boiler installation would cost for your home in Sussex or Surrey, we'll give you a full, itemised quote — free, and with zero obligation.