How Much Does Gas Boiler Installation Cost? (UK)
A new gas boiler is a big-ticket home job, so it pays to know the ranges. In 2026, gas boiler installation in the UK costs £1,800-£3,500 for a like-for-like combi swap, £2,500-£4,000 for a system boiler, and £3,500-£5,500+ for a full conversion or a boiler relocation. Price depends on boiler type and output, brand, and how much pipework changes. This guide breaks it down and shows how to compare Gas Safe quotes.
Gas Boiler Installation Cost by Job Type
The two big drivers are the boiler itself (type, output and brand) and the labour, which depends on whether it is a straight swap or a conversion with new pipework and controls. All gas work must be done by a Gas Safe registered engineer. Here is the 2026 ladder.
Like-for-like combi swap
£1,800-£3,500 fitted. Replacing an existing combi in the same spot - the most common and cheapest job. Includes boiler, fitting, a flush and basic controls.
System boiler (with cylinder)
£2,500-£4,000. For homes with a hot-water cylinder and higher demand. More pipework and controls than a combi swap.
Conventional / heat-only
£2,500-£4,200. Traditional system with tanks and cylinder, often in older or larger homes. Sizing and controls add to the cost.
Conversion or relocation
£3,500-£5,500+. Changing boiler type (e.g. conventional to combi) or moving the boiler needs new pipework, flue and possibly a bigger gas supply.
Boiler brand & output
Premium brands and higher outputs cost more but often bring longer warranties (up to 10-12 years). Correct sizing matters more than paying for excess output.
What the price includes
Boiler, flue, fitting, a system flush (often a power flush £300-£600 if needed), controls/thermostat, commissioning and Gas Safe / Building Regs notification. Confirm each is in the quote.
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