We use cookies to allow us and selected partners to improve your experience and our advertising. By continuing to browse you consent to our use of cookies as per our policy which also explains how to change your preferences.

New Boiler: What You Need to Know Before you Buy a New Boiler

The Cost of Installing a Boiler

By Matthew Knight

Article 6 of 7

Find out how to get a new boiler installed and how much it should cost. We'll help make sure you don't get overcharged for your boiler installation.

Put us to the test

Our Test Labs compare features and prices on a range of products. Try Which? to unlock our reviews. You'll instantly be able to compare our test scores, so you can make sure you don't get stuck with a Don't Buy.

The cost of installing a new or replacement boiler is expensive, and installers' quotes can vary. So you need to know what to expect before you contact a qualified boiler engineer.  

Our guide to boiler installation prices will make sure you know what to expect to pay, so you don't end up paying over the odds. This isn't a job you can do yourself to cut costs, unless you're a Gas Safe registered installer.

But before you sign up to a new boiler, make sure you're getting a reliable brand. Every year, we survey thousands of boiler owners and hundreds of heating engineers so we can tell you which brands make the best and most reliable boilers. 

Rated: the best boilers that Which? recommends.

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, which allowed those with an inefficient boilers to claim back cash to help them pay for a new boiler, a freedom of information request revealed energy companies were charging, on average, around a third more than independent traders. 

We've teamed up with the Association of Plumbing and Heating Contractors (APHC) to show you the typical scenarios you might face and how much you should expect to pay for installation only. Once you have read about the cost of installation, see our guide to typical boiler prices

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

This job involves removing and disposing of the old 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. This procedure should prolong the life of any new boiler.

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. This 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 to £300 to the cost. Very old systems may require a mechanical flush before installation - this costs around £510.

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 to £1,440

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 combi 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 £1,440 for a basic job

You may need additional pipe work (around £200 to £300) and a chemical (about £200) or mechanical flush (around £510) of your heating system.

Finding a registered boiler installer

Which? Trusted Traders should be your first port of call for finding a registered boiler installer. All Which? Trusted Traders must meet our high standards in order to register on the Trusted Trader scheme, and so they are a great place to start to look for a high quality installation, service or repair to your boiler.

Before you call an installer, make sure you've got a good grounding in what to expect when you get a new boiler. Check out our quick and easy guide - 5 things you need to know before you buy a new boiler. If you are unsure what type of boiler you need, take a look at our guide to combi boilers

Gas installations by the Gas Safe Register

The Gas Safe website can also provide details of registered installers in your area. Alternatively, call Gas Safe on 0800 408 5500. 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 oil systems 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 schemes, listed below, exist to help you track down a suitable competent person for oil appliances. You can find more details on these websites:

  • www.aphc.co.uk (Association of Plumbing and Heating Contractors (Certification) Limited 0121 711 5030
  • www.besca.org.uk (BESCA Limited) 0800 652 5533
  • www.napit.org.uk 0870 444 1392
  • www.niceic.com 0800 013 0900
  • www.oftec.org.uk 0845 658 5080