Which? Reviews No advertising, no bias, no hidden agenda

Boiler reviews: Installation

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 Safe Card

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:

A man installs a boiler

Boiler installation costs will depend on how complicated it is

Installation costs

Installation costs will vary enormously depending on how much work is required. We've drawn up four examples which show typical scenarios you might face, and how much you should expect to pay in each.

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, then cleansing and flushing out the heating system before installing the new boiler.

Expect to pay Around £600

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

The fitter will need to add extra plumbing, including a condensate drain, and cleanse and flush out the heating system.

Expect to pay Around £750 to £850

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 jobs such as adding a condensate drain and routing the flue.

Expect to pay Around £1,500 to £1,800

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. Replumbing and adding a condensate drain will also boost costs.

Expect to pay Around £2,000 to £2,200