Boilers: Installing a boiler

Boiler installation

Get quotes from a number of different boiler installers

Boiler installation costs

Boiler installation costs vary enormously depending on how much work is required, the parts needed and their availability, where you live and who you employ for the job.

Following the boiler scrappage scheme in 2010, a freedom of information request revealed energy companies were charging, on average, around a third more than independent traders.

We've teamed up with APHC (Association of Heating and Plumbing Contractors) to show typical scenarios you might face, and how much you should expect to pay for installation only.

Replacing an existing gas condensing combination boiler in the same position as the previous one

This job involves removing and disposing of the previous boiler before installing the new one. 

Expect to pay Around £540 - £660

If your heating system is very old it may need a mechanical flush, which costs around £510. This involves cleaning the heating system by adding chemicals which are flushed through the pipes with an external pump.

Replacing a gas non-condensing boiler with a condensing one, in the same position

Before installing a combi boiler the fitter will need to check the gas supply and position of the flue, which may need to be removed or replaced to fit the new boiler. 

Expect to pay Around £640 to £770 

Moving pipes will add around £200 - £300 to the cost

Very old systems may require a mechanical flush prior to installation.

Installing a new gas condensing boiler in a different location and upgrading your heating system by adding radiator valves and changing the controls

This involves complex plumbing work such as adding a condensate drain and routing the flue.

Expect to pay Around £1,140 - £1440

The system will also need a chemical flush, which involves adding cleaning chemicals to the heating system to remove debris. This costs around £200.

Trading in a gas heat-only boiler for a condensing combination boiler

The fitter will need to convert your system from an open-vented setup to a sealed one. This will involve removing obsolete equipment, such as the hot water storage cylinder, cold water storage tank and the feed and expansion tank in the loft. Re-plumbing and adding a condensate drain will also boost costs.

Expect to pay Around £1440 for a basic job

You may need additional pipe work (around £200-£300) and a chemical or mechanical flush of your heating system.

Gas Safe Card

Ask to see your engineer's Gas Safe Register ID card

Finding a registered installer

Any new gas or boiler needs to be fitted by a competent person in accordance with the Building Regulations and Gas Safety (Installation and Use) Regulations.

Gas installations by the Gas Safe Register

The easiest way to ensure this is to employ a Gas Safe registered installer to do it for you. Previously you should have used a Corgi (Council for Registered Gas Installers) registered installer, but the requirement changed in April 2009. Gas Safe can provide details of registered installers in your area. Each installer must carry an ID card, which lists the gas work they are qualified to do.
Check it covers the work you're expecting and includes the words 'energy efficiency'. You can also check their registration with Gas Safe.

Oil boiler installations

Installation of the following are all work that should be carried out by a competent person:

  • An oil-fired combustion appliance which has a rated heat output of 100kW or less, and which is installed in a building with no more than three storeys (excluding any basement) or in a dwelling.
  • Oil storage tanks and the pipes connecting them to combustion appliances.
  • Heating and/or hot water service systems connected to an oil-fired combustion appliance.

Several competent persons schemes for oil appliances exist. You can find more details in their web pages:

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