If you’re replacing an existing combi boiler with a new one, you can expect to pay around £1,800 to £3,500 for a typical supplied-and-fitted replacement in 2026, although the actual cost depends on the boiler you choose and the work required in your home.
A straightforward like-for-like replacement is usually the least expensive option. If you want to move the boiler, increase its output, change the heating system or upgrade other components at the same time, the price can be considerably higher.
A combi, or combination, boiler provides central heating and hot water from one appliance. Unlike a system or regular boiler, it doesn’t need a separate hot water cylinder.
Replacing a combi boiler means removing the existing appliance and installing a new one, usually in the same location.
If the new boiler is a similar size and can use the existing pipework and flue arrangement, the installation can be relatively straightforward.
As a general 2026 guide, a like-for-like combi boiler replacement may cost approximately:
| Type of installation | Indicative cost |
|---|---|
| Basic like-for-like replacement | £1,800–£2,500 |
| Mid-range replacement | £2,300–£3,200 |
| Premium replacement | £2,800–£3,500+ |
| Replacement involving relocation or significant alterations | £3,000–£4,500+ |
These are indicative UK prices rather than quotations. Published 2026 cost guides show a wide range, which reflects differences in boiler specification, labour, location and the condition of the existing heating system.
The best way to compare prices is to make sure you’re comparing like-for-like quotations that include the boiler, installation, controls, flue, commissioning and any necessary system work.
Boilers are available at different price points. A basic model may cost considerably less than a premium boiler with additional features or a longer manufacturer’s warranty.
Don’t automatically choose the cheapest boiler. Consider the boiler’s output, warranty, efficiency, controls and whether there is suitable manufacturer support in your area.
A larger boiler isn’t necessarily a better boiler.
The correct size depends on the heating requirements of your property and, importantly for a combi, your hot water demand.
For combi boilers, the hot water output can be particularly important because the boiler has to heat mains water as you use it.
Keeping the replacement boiler in the same position can reduce installation time and the amount of new pipework required.
Moving the boiler means additional work involving pipework, the flue, condensate drainage and potentially electrics.
An old heating system may need additional work before a new boiler is installed.
For example, an engineer may recommend cleaning the system, replacing damaged components, upgrading pipework or fitting a magnetic filter.
This isn’t necessarily a sign that you’re being sold extras. The new boiler has to work with the existing heating system, and an installer should assess its condition before deciding what is required.
Replacing the boiler can be a good opportunity to review your controls.
Modern heating controls can include programmers, room thermostats, smart thermostats and thermostatic radiator valves. Good controls allow the heating system to operate only when and where heat is needed.
Usually, yes.
Replacing a combi with another combi is generally simpler because the existing hot water and heating arrangements can remain broadly the same.
Changing from a regular or system boiler to a combi is a much bigger project because the hot water cylinder, tanks and associated pipework may need to be removed or altered.
For example, Which? estimates that changing from a heat-only or system boiler to a combi can add around £400–£800 in extra labour and repiping, although the overall cost varies by property.
A repair can make sense if the boiler is relatively young and the fault is straightforward.
Replacement may be worth considering if:
There isn’t a single age at which a boiler must be replaced. The condition and repair history matter just as much as its age.
A straightforward like-for-like replacement can often be completed in around a day.
More complicated installations can take longer, particularly if the boiler is being moved or you’re changing from one type of heating system to another.
Your installer should tell you how long they expect the work to take before the installation begins.
For many homes, a modern combi can be a convenient replacement because it provides heating and hot water from one compact appliance.
However, a combi isn’t right for every property.
If you have multiple bathrooms, low mains water pressure or high simultaneous hot water demand, a system boiler with a hot water cylinder may be a better option. Energy Saving Trust similarly notes that combis can be less suitable for homes with multiple bathrooms or low water pressure.
The short answer
A combi boiler replacement typically costs around £1,800–£3,500 in 2026, but the final price depends on the boiler, its size, your existing system and whether additional work is required.
A like-for-like replacement in the same position is usually the simplest and cheapest option.
A typical like-for-like replacement can cost around £1,800–£3,500 supplied and fitted, although prices vary according to the boiler and installation requirements.
A straightforward replacement can often be completed in one day. More complicated installations can take longer.
Yes, but the correct boiler size should be determined by the heating and hot water requirements of your home rather than simply choosing the largest available model.
Yes, in many homes. However, moving a boiler involves additional pipework and flue and condensate considerations, so it usually increases the installation cost.
Not necessarily. An installer should assess the existing heating system and advise whether the radiators are suitable for the new boiler and the heating requirements of the property.
Gas work on domestic gas appliances must be carried out by a suitably qualified Gas Safe registered engineer.
