Cost calculator
Boiler installation cost calculator
A boiler swap and a system conversion are very different jobs sold at similar-sounding prices. What matters is whether the quote includes a proper flush, new controls, and the pipework changes your system actually needs.
Bedroom count is a good proxy for boiler output and radiator circuit size.
Broad trade availability keeps day rates near the national average.
Estimated range, ex VAT
£2,450 – £5,250
- Labour (typical)
- £1,600
- Materials (typical)
- £2,250
Guidance only. A real quotation depends on site conditions, specification and access — which is exactly what an independent review of your own quote will tell you.
What affects the cost
Like-for-like vs conversion
Swapping a combi for a combi in the same place is the cheapest option. Converting from a system or back boiler adds tanks, pipework and days.
Boiler brand and output
Budget and premium brands differ by £600–£1,200 on the appliance alone, and by several years on warranty.
Moving the boiler
Relocating to a different room means new gas, condensate, flue and pipe runs — often £700–£1,500 extra.
Flue route
Flues needing scaffolding, roof terminals or a plume kit add cost and sometimes another visit.
Controls and compliance
Boiler Plus requires load or weather compensation, a smart thermostat or flue gas heat recovery on new combi installs.
Regional pricing differences
Materials cost roughly the same everywhere in the UK; labour does not. Use the region selector above to apply a local index — London and the South East typically run 15–30% above the national average, while the North East, Northern Ireland and Yorkshire sit below it.
Labour vs materials
Roughly 42% of this type of work is labour and 58% materials. One to two days of Gas Safe labour plus the appliance. Controls, filters and a power flush add both labour and parts.
Common hidden costs
- System flush or magnetic filter, sometimes offered as an optional extra when it should be standard.
- Gas supply pipe upgrade where the existing 15mm run cannot deliver the required volume.
- Condensate drain routing to an internal soil stack — external runs freeze and fail.
- Making good tiling and plasterwork where the old appliance sat.
How to save money
- Install outside the October–January peak; prices and lead times both improve.
- Choose a mid-range brand with a 10-year warranty rather than a premium badge with 7.
- Keep the boiler in the same location unless there is a strong reason to move it.
- Confirm the warranty requires annual servicing and who is registering it — you or the installer.
Frequently asked questions
How much is a new boiler installed in the UK?
A like-for-like combi replacement typically costs £2,200–£3,600 fitted; a conversion from a system boiler £3,500–£5,500.
How long does a boiler installation take?
One day for a straightforward swap, two to three days for a conversion or relocation.
Do I need a power flush?
On an older system with radiator sludge, yes — and most manufacturer warranties require the system to be cleaned to BS 7593.
Must the installer be Gas Safe registered?
Yes, by law, and they must notify the installation to building control through the Gas Safe scheme.
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