How Much Does It Cost to Replace a Boiler?

These are Vector Heat's installed guide prices, not a national average or a fixed quotation for your house. They cover the replacement route shown, before additional work identified at the survey. A new cylinder, oil tank or set of radiators is not included.

The first thing to check with any new boiler installation cost is whether you are looking at the boiler on its own, a fitted replacement, or a conversion to a different system. They are three different purchases.

Gas and LPG Boiler Replacement Prices

A like-for-like replacement keeps the same basic arrangement. A combi replaces a combi, or a regular boiler replaces a regular boiler while keeping the cylinder. There can still be work to the flue, controls or pipework, but you are not removing the hot-water storage system.

The boiler model and output make a substantial difference to the price. The ranges below cover the options currently offered by our quote tool for each type of job. Both ends of each range include installation. The cheapest option still needs to suit your home; extra work on the flue, pipework or heating system is priced separately.

Installed guide prices updated 20 September 2026, including VAT and before optional flue or power-flush extras. They are not a maximum price for every installation. The same-position replacement prices assume a standard horizontal flue, the existing flue opening and suitable existing condensate drainage. Boiler availability and work identified at survey can change the final quote.

Keeping a cylinder does not necessarily mean keeping a header tank. The regular-to-system price for a header-tank arrangement includes pressurising the heating system. If it is already pressurised, that work is not needed. An existing system boiler has its own replacement price, rather than a conversion charge added on top.

How Much Is It to Install a Combi Boiler?

Replacing an existing gas combi starts at £1,918 in our current guide prices. Converting a boiler-and-cylinder arrangement to a combi starts at £2,398. The conversion costs more because we remove the cylinder, alter the pipework and adapt the heating and hot-water arrangement, rather than just replacing the boiler.

For example, one of our gas combi options has an installed replacement price of £2,201. The extra conversion work and pipe allowance add £480, bringing the guide total to £2,681 including VAT. If the system needs the additional power-flush option, that adds £350 during the installation, making £3,031. All these figures include VAT. This is a worked guide example, not a fixed price for every conversion.

With an older open-vent system, we also need to assess how the existing pipework and radiators will cope when pressurised. A back boiler behind a gas fire, or a boiler moving to another room, needs its own surveyed quotation.

A combi is not automatically an upgrade for everyone. If you use several bathrooms at once, keeping a suitable cylinder can be the better decision. I look at your mains water supply and actual hot-water use before recommending that we take it out.

Nor should you buy the biggest boiler simply because the price difference looks small. Heating output and hot-water performance are different things. Our boiler sizing guide explains what we calculate and why bedroom count is only a rough starting point.

How Much Does an Oil Boiler Replacement Cost?

Our oil replacement guide prices start at £3,729 for an indoor heat-only boiler keeping the existing cylinder. An indoor oil combi starts at £4,888. Whether the appliance is inside or outside, and whether you keep stored hot water, makes a substantial difference to the price.

The move-outside and conversion rows include the additional installation allowances for those jobs. The survey still needs to confirm the base, pipe routes and any other work required; these figures are not a fixed quote for every move. A new oil tank is a separate item, even when it makes sense to replace it during the same project.

The cylinder-retained oil prices are for a regular, heat-only replacement. If your existing oil boiler is a system model, we will check the replacement arrangement and any additional components at survey.

Oil boilers are heavy. We have two people moving them, with floors, doors and the route through the house protected. That does not automatically make the installation a two-day job: a straightforward oil swap is normally completed in one day by the team.

The survey needs to include the oil supply, tank condition, base, flue and access. You can find more about that on our oil boiler replacement in Lincolnshire page.

What Changes the Cost of a Boiler Installation?

The biggest changes come from moving the boiler, changing the hot-water arrangement, difficult flue routes and work needed elsewhere on the system. Two houses getting the same model can need quite different installations. The survey is where we separate a straightforward replacement from those additional jobs.

Boiler Position and Flue

Keeping the boiler in the same position is generally simpler. Moving it means extending or rerouting heating, hot-water, fuel and condensate pipework, as applicable. We also need a suitable flue position.

Using the existing hole does not mean the old flue can be reused. The new boiler needs its correct approved flue system. A roof route, scaffolding or making good an old opening should be discussed and included where required.

Condensate, Fuel Supply and Controls

Replacing a non-condensing boiler means providing a condensate drain. An existing drain may also need improving. Gas pipework must supply the chosen appliance properly, while controls need to suit the boiler and how you use the house.

These details are easy to miss when comparing two boiler model names. They are also much easier to agree before the engineer has started taking the old boiler off the wall.

Pumps, Valves, Cylinders and Radiators

A replacement boiler does not make a worn-out pump new again. If components need changing, we should identify them and price them. Keeping a sound cylinder or radiators is perfectly reasonable; replacing everything just because the boiler is new is not.

If you want extra radiators, a replacement cylinder or a shower conversion, ask for those as separate items. Otherwise, one quote for a boiler swap can look cheaper than another quote that includes half the heating system.

System Cleaning and Power Flushing

The system needs to be properly cleaned for the new boiler, but not every installation needs a power flush. I look at the water condition, radiator performance and the system's history. An old open-vent system full of debris is a different job from a clean sealed system.

Our quote tool currently allows £350 for an additional power flush carried out with the boiler installation. That is not a standalone power-flushing price, and it is not an automatic addition to every job. The cleaning method and scope should be agreed after assessment.

We fit magnetic filters, but a filter is not a substitute for getting the system clean in the first place.

How Much Should It Cost to Replace a Boiler?

A fair comparison is the total installed price for the same work, including VAT, the actual boiler model and agreed extras. The cheapest number is only meaningful once those things match. Ask each installer to confirm what is included, what is excluded and what could change after the survey.

After 14 years of surveying heating systems, I would rather spend a little longer checking the job than give you a cheap headline price that grows once work starts.

A boiler-only internet price is not an installation quote. It does not include someone assessing the system, fitting the appliance, commissioning it and taking responsibility for the work.

Repairing an Older Boiler Can Still Make Sense

Before spending money on a replacement, find out what is actually wrong with the existing boiler. Age matters, but condition, repair history and parts availability matter too.

A well-maintained older boiler with one repairable fault is different from one that has needed expensive repairs every year. Ask your engineer what condition it is in, whether the common failure parts have already been replaced and what further work is likely.

Our guide to how long boilers last explains that decision. I would not tell you to replace a working boiler purely because it has reached a particular birthday.