Boiler installation across the South West

Signs you need a new boiler

Boilers rarely give up without warning. Manufacturers put a well-maintained boiler's life at around 10 to 15 years, so if yours is older than that and showing any of the signs below, it makes sense to price a boiler replacement now rather than in the first cold snap. Replace your boiler on your own timetable and you can pick the right model instead of whatever is available that week.

Our guide on how long a boiler can last goes into more detail on age, parts and efficiency.

• The same fault keeps coming back, or you have had several breakdowns in a year
• Parts are getting hard to find, or a repair quote is creeping towards the cost of a new boiler
• Gas bills keep rising even though you use the heating the same way
• Radiators take ages to warm up, or the hot water runs hot and cold
• Soot marks on the case or a lazy yellow flame: switch it off and get a Gas Safe engineer to check it

Choosing the type and size of boiler

Every new gas boiler is a condensing boiler. It recovers heat from the flue gases that older models sent straight outside, which is why a modern one burns less fuel for the same warmth. The real choice is between a combi, a system or regular boiler, and the table above sets out the differences.

Boiler size is measured in kilowatts. A combi is sized on the hot water flow your household needs; a system or regular boiler is sized on the heating needs of the whole house. Too big wastes money and makes the boiler cycle on and off. Our boiler size guide explains the numbers, and the survey settles them for your home.

Changing boiler type is common. Moving from a regular boiler with a cold water tank in the loft to a combi frees up space, but only works if your mains pressure and flow can supply the taps and showers you use at the same time. Off the gas grid? We can fit an oil boiler instead.

What happens on the day of installation

Fitting a new boiler starts with protecting the floors and the route to the boiler. Your heating engineer then drains the heating system and disconnects the old boiler.

The new boiler, flue and controls go in next. On a like-for-like swap most of the pipework stays where it is. A relocation or a switch to a different type adds work, which is why those jobs take longer. Relocating the boiler, say from the kitchen to a utility room or loft, is covered on our boiler relocation page.

Before the engineer leaves, the central heating is cleaned and refilled with inhibitor, a magnetic filter goes on, and the boiler is commissioned and tested. You get a walk through the controls and all the paperwork.

How much does a new boiler cost?

Which? puts the cost of a new boiler, fully installed, at around £1,400 to £7,000. Those are market figures, not our prices: we give you one fixed price after a free survey, and finance is available, subject to status, if you want to get a new boiler now and spread the payments.

Where your job lands in that range comes down to the type of boiler, its output and the complexity of the job:

• The boiler itself: make, model and output
• The flue: a short flue straight through an outside wall is simpler than a long or vertical one
• Gas supply: Which? puts upgrading the gas pipe for a bigger boiler at £100 to £400
• A new position or a different type of boiler, which means new pipework
• Extras such as a new cylinder or a power flush (see the table above)

The paperwork you should get

Installing a new boiler is notifiable work: every gas boiler installation has to be done by a Gas Safe registered engineer and notified under Building Regulations. Our engineers notify the job for you, and Gas Safe Register then issues a Building Regulations compliance certificate to the homeowner.

The engineer also fills in the Benchmark checklist in the boiler manual, which records the commissioning details and the installation date. Keep both. You will need them for warranty claims and when you sell the house.