A new boiler installation typically costs £2,500 – £4,000 in the UK for a straightforward combi replacement, including the boiler and fitting. Converting from an older heating system or moving the boiler can push the price above £4,000.

According to the Energy Saving Trust, replacing a G-rated gas boiler with an A-rated model and thermostatic radiator valves costs around £3,500 on average in Great Britain.

However, the price you actually pay depends on more than the boiler itself. Your existing heating system, installation location, pipework and choice of heating controls can all affect the final quote.

We’ve broken down current UK boiler fitting costs to help you understand what’s reasonable, what’s included and where you could save money.

How much does it cost to install a new boiler in 2026?

The most useful way to compare installation prices is by the type of work required.

Replacing an existing combi boiler in the same position is generally cheaper than converting a system boiler or removing an older hot water cylinder.

Installation type	Typical fitted cost
Combi-to-combi replacement	£2,500–£4,000
Regular boiler to combi conversion	£3,000–£4,500
System boiler to combi conversion	£3,000–£4,500
Combi to system boiler conversion	£3,200–£4,800
Back boiler to combi conversion	£4,000–£6,000+

Indicative UK estimates based on published 2026 pricing. Figures include the boiler and installation, but actual quotes depend on the property, specification and any additional work. VAT should be confirmed with the installer.

A straightforward replacement will usually sit towards the lower end of these ranges, while older properties and more complicated installations can cost considerably more.

The important distinction is between the price of a new boiler and the cost of having it fitted. A cheaper appliance doesn’t necessarily mean a cheaper installation if significant alterations are required.

Combi boiler replacement costs

Replacing an existing gas combi boiler with another combi typically costs £2,500–£4,000, supplied and fitted.

This is often the simplest installation because the property already has the basic heating arrangement in place.

For a straightforward swap, the engineer will usually remove the existing boiler, fit the replacement, connect the appropriate services, clean and protect the heating system, and complete the necessary safety checks.

However, a like-for-like replacement doesn’t automatically mean no additional work.

For example, an older boiler may have an unsuitable flue arrangement, inadequate gas supply pipework or missing modern heating controls. Any of these could increase the installation cost.

A replacement boiler also needs to be correctly sized. Choosing a more powerful model simply because your previous boiler had a high output isn’t necessarily the best decision.

In many homes, the hot water demand determines the output required from a combi boiler, while the heating side may need substantially less power.

Our advice: Compare quotations using the same boiler model, warranty, filter, controls and installation scope. Otherwise, what looks like a £500 saving might simply be a less comprehensive installation.

How much does it cost to convert to a combi boiler?

Converting from a regular or system boiler to a combi typically costs around £3,000–£4,500, although complicated installations can exceed this.

The additional expense comes from changing how the heating and hot water systems operate.

A regular boiler may have a cold water storage tank in the loft and a separate hot water cylinder. Replacing it with a combi can involve removing redundant equipment, altering pipework and connecting the new boiler directly to the mains water supply.

A system boiler conversion is similar, although the existing plumbing arrangement may be less complicated.

Converting to a combi can free up cupboard or loft space, but it isn’t automatically the best option.

Combi boilers heat hot water on demand, so their performance depends partly on the available mains water flow rate and pressure.

For homes with multiple bathrooms used simultaneously, retaining a hot water cylinder may be a better solution.

Before recommending a conversion, an installer should assess your household’s hot water requirements and test the water supply.

How much does boiler installation labour cost?

Boiler installation labour and fitting services typically cost around £1,000–£2,000, although complex conversions or extensive alterations can cost more.

This is separate from the cost of purchasing the boiler.

Labour charges depend on several factors, including the time required, whether multiple engineers are needed and the amount of plumbing or electrical work involved.

A straightforward installation could be completed within a working day. More complicated conversions may require two or three days.

Some installers provide fully inclusive fitted prices rather than separating every component. This is perfectly reasonable, provided the quote clearly identifies what’s included.

Bear in mind that buying a boiler separately and paying an independent installer to fit it doesn’t guarantee a lower total price. Installation companies may have access to manufacturer discounts, extended warranties and bundled components.

If you’re comparing supply-only and fitted prices, make sure you’re accounting for all the necessary materials, commissioning and associated work.

What’s included in a new boiler installation?

A standard boiler replacement should cover more than simply installing a new appliance on the wall.

Depending on your existing system and the installation package, the quotation should specify:

• Removal and disposal of the old boiler.
• Supply and installation of the new boiler and suitable flue.
• Required pipework and connections.
• Heating system cleaning and appropriate water treatment.
• A magnetic system filter, where included or required.
• Compatible heating controls.
• Safety checks, commissioning and relevant paperwork.
• Manufacturer warranty registration and any applicable Building Regulations notification.

Not every company includes the same work as standard, so don’t assume that two similarly priced quotations offer an identical package.

One particularly important consideration is system cleanliness.

Installing a new boiler onto an existing heating system containing sludge or debris can affect performance and may compromise warranty conditions.

Your engineer should assess the condition of the heating system and recommend an appropriate cleaning method, rather than automatically adding an expensive power flush to every quotation.

What additional costs can increase boiler installation prices?

It’s common for a boiler replacement to reveal work that wasn’t immediately apparent when the initial price was calculated.

Here are some additional costs worth checking.

These are guide prices, not guaranteed extras. Some may already be included in a fixed-price installation quote.

Gas pipework and flue alterations

Older gas pipework may need upgrading if it cannot safely supply the new boiler.

However, 15mm gas pipework does not automatically need replacing with 22mm pipework. The appropriate size depends on the appliance requirements, pipe length, fittings and permissible pressure drop.

The installer must check the gas supply and determine whether alterations are necessary.

Flue changes can also increase costs, particularly when moving the boiler or changing the flue route.

Heating controls and system upgrades

A new boiler is also an opportunity to improve how your heating system operates.

Modern controls can help manage room temperatures and heating schedules more effectively. Certain controls can also adjust the boiler’s operation to improve efficiency.

However, you don’t necessarily need the most expensive smart thermostat available.

A properly configured heating system with suitable controls can be more useful than a feature-packed thermostat that isn’t compatible with your boiler’s advanced functions.

Check whether new thermostatic radiator valves, upgraded controls or additional radiators are actually required before agreeing to extra work.

What makes one boiler installation quote more expensive than another?

Two installers can quote very different prices for what appears to be the same boiler replacement.

Some differences are straightforward. A premium boiler model or longer manufacturer warranty may cost more.

Others are less obvious.

For example, one quote may include a magnetic filter, full system cleaning, upgraded controls and removal of the old boiler. Another might only cover the basic replacement, with those items charged separately.

The installation itself also matters.

An experienced engineer should assess the heating requirements, water flow, flue arrangement and existing pipework before recommending a suitable boiler.

One detail worth asking about is boiler commissioning and heating flow temperature.

Modern condensing boilers operate more efficiently when the heating system can run at lower return-water temperatures.

As the Energy Saving Trust explains, carefully reducing the heating flow temperature can improve efficiency, provided the system can still heat the property adequately.

That makes correct setup important. A boiler fitted quickly but left operating inefficiently may cost more to run over its lifespan.

For systems with a separate hot water cylinder, temperature settings also need to account for safe hot water storage.

How long does it take to fit a new boiler?

A straightforward combi-to-combi replacement is usually completed within one working day, with uncomplicated installations sometimes taking around four to six hours.

More involved work can take longer.

Installation	Typical duration
Like-for-like combi replacement	Usually one working day
Regular boiler to combi conversion	Around 1.5–2 days
System boiler to combi conversion	Up to 3 days
Boiler relocation	Depends on the extent of the work

The engineer should explain how long you’ll be without heating and hot water before work begins.

Older properties may also require additional time for alterations to pipework, flues or associated heating components.

How to compare boiler installation quotes

The Energy Saving Trust recommends obtaining at least three quotations when replacing a boiler.

However, simply selecting the cheapest isn’t necessarily the best approach.

Instead, compare the complete installation package and the suitability of the proposed boiler.

Before accepting a quote, establish whether the installer has included all necessary work, the warranty offered, any exclusions and the total cost including VAT where applicable.

For gas boilers, use an engineer who is registered with the Gas Safe Register and qualified for the work involved.

Ask how the installation will be notified under the applicable Building Regulations and what commissioning and compliance paperwork you’ll receive.

You should also ask whether annual servicing is necessary to maintain the manufacturer’s warranty, and whether any specific installer or product registration conditions apply.

If you’re uncertain about the price, EnergyGuide’s boiler installation cost calculator can provide another starting point before requesting quotations.

Can you get a grant towards boiler installation?

Government support depends on your circumstances, the heating system being installed and where you live.

ECO4 funding

The Energy Company Obligation scheme (ECO4) supports eligible households with qualifying energy efficiency and heating improvements.

It targets households experiencing fuel poverty or other qualifying circumstances, but it is not a general grant available to everyone replacing an older boiler.

ECO4 has been extended to 31 December 2026, according to Ofgem.

Eligibility and the measures available depend on the property’s circumstances and the scheme rules.

Boiler Upgrade Scheme

The Boiler Upgrade Scheme is different. It supports eligible low-carbon heating systems rather than conventional replacement gas boilers.

In England and Wales, eligible property owners can receive grants including:

• £7,500 towards an air-to-water air source heat pump.
• £7,500 towards a ground source heat pump.
• £5,000 towards an eligible biomass boiler.
• £2,500 towards an air-to-air heat pump.

Additional support may be available in certain circumstances.

Full eligibility requirements are available on GOV.UK.

If you’re planning to replace an ageing gas or oil boiler, comparing the cost of a replacement boiler with a grant-supported heat pump is worth considering before committing.

Households in Scotland and Northern Ireland should check the funding schemes available in their respective nations.

Is it worth replacing your existing boiler?

A newer boiler can improve heating reliability and efficiency, particularly when replacing a considerably older, inefficient appliance.

But replacement isn’t automatically the right decision simply because a boiler has reached a particular age.

If your existing boiler is working reliably, is reasonably efficient and can be repaired economically, continuing to maintain it may make better financial sense.

On the other hand, frequent breakdowns, expensive replacement components, poor efficiency and declining reliability can make a new installation more attractive.

It’s also important to consider the wider heating system.

Poorly balanced radiators, unsuitable controls or a badly configured boiler can all contribute to high heating costs, even if the boiler itself is relatively modern.

Before spending several thousand pounds, it pays to establish whether the boiler is genuinely the problem.

For more information about available models and purchase prices, see our separate guide to new boiler costs in the UK.

FAQs on How Much to Fit A New Boiler

What Is The Cost Of Fitting A New Boiler?

In 2026, the average cost to supply and fit a new boiler in the UK ranges between £1,800 and £4,800, depending on the type of boiler and the complexity of the installation. The Energy Saving Trust places the typical figure for an A-rated gas boiler with thermostatic radiator valves at around £3,700.

How Much Is A Boiler Service In 2025?

A standard annual gas boiler service costs between £80 and £120 in 2026, based on average prices. This includes safety checks, cleaning, and performance testing carried out by a Gas Safe-registered engineer.

How Much Is A New Boiler For A Three-Bedroom House?

A typical three-bedroom home in the UK usually needs a 24–30 kW combi or system boiler. The full installation cost generally falls between £2,500 and £3,800, depending on the brand and whether any pipework or controls need upgrading.

How Long Does It Take To Fit A New Boiler?

A like-for-like boiler replacement usually takes one working day. Conversions, such as changing from a regular or system boiler to a combi, can take two to three days, especially if new pipework or a flue relocation is required.

What Size Boiler Do I Need For A 4 Bedroom House?

Most four-bedroom homes require a boiler with an output of 30–40 kW, depending on the number of bathrooms and radiators. System boilers are often recommended for larger properties with higher hot-water demand.

Sources and References

• GOV.UK – Boiler Upgrade Scheme