UK quote-led budget · reviewed September 2026

Boiler replacement cost calculator.

Turn a written gas-boiler quote and any work priced outside it into one complete budget. No postcode, email or invented regional multiplier.

Build the complete replacement budgetStart with a written VAT-inclusive quote where possible.

Step 1 of 2

Proposed replacement

Home nation

Building rules, notification routes and support differ across the UK.Proposed gas boiler

Installation change

The choice raises scope checks; it does not apply a made-up percentage multiplier.

Quote and separately priced work

Main installer quote or planning figure

Starts at Energy Saving Trust's current £3,500 Great Britain average. Replace it with your own complete quote.Controls

Radiators and valves

Cylinder or tank work

Gas or electrical work

Flue or condensate work

Making-good or other work

Enter an extra only when it is outside the main quote. Ask whether removal, system cleaning, inhibitor, filter, commissioning, certification and VAT are included.

Confirmed support or discount

Amount confirmed in writing

Leave at £0 unless the contribution is real and documented. This calculator cannot decide ECO or local-scheme eligibility.

Example replacement budgetFree result. No postcode or contact details required.

Step 2 of 2

Budget after entered support

£3,500Before finance, servicing, fuel or unquoted work

Project before support£3,500Main quote plus separate extras

Confirmed support entered−£0Capped at the project total

Separate work entered£0Do not duplicate quote inclusions

Main installer figure£3,500Visitor-entered price source

Checks raised by your choices

The £3,500 starting figure is Energy Saving Trust's current Great Britain average; replace it with an itemised written quote for your property.
No separate extras are entered. Check whether controls, valves, system cleaning, flue/condensate work, certification and making-good are included in the main quote.

Calculation boundaries

Every cost is entered by the visitor and should include VAT where applicable.
Extra-work fields should contain only items not already included in the main installer quote.
No regional, boiler-type or relocation multiplier is invented; the written quote remains the price source.
Any support discount is a budgeting input, not confirmation of ECO eligibility, funding or availability.

Budget, not a quotation or safety check

Gas work must be done by a suitably qualified Gas Safe registered engineer. Verify the engineer's relevant competencies, get the scope in writing and retain commissioning and building-compliance documents.

After your free estimate

Want an exact local price?

A written survey scope is needed to price the boiler, controls, pipework, flue, condensate route, cleaning, certification and making-good.

Optional. Your estimate stays visible. We'll use a short qualification step so unsuitable or out-of-area requests are not passed around.

How the calculation works

The written quote is the price source.

The model adds the main installer figure to any separately entered controls, radiators, cylinder, gas/electrical, flue/condensate and making-good work. A confirmed support figure is then subtracted, capped at the project total.

The £3,500 starting point is Energy Saving Trust's current average for a Great Britain gas-boiler replacement with thermostatic radiator valves. Categories such as relocation and system change raise visible scope questions but never apply an unsupported percentage.

What changes the result

Factors worth checking before you decide.

Combi, system or regular boiler layout and hot-water demand.

Like-for-like replacement, relocation or a change of system type.

Gas supply, electrics, pipework, flue and condensate route.

Controls, radiators, valves, cylinder, system cleaning and filter.

Removal, access, scaffolding, commissioning, certification and making-good.

VAT, written exclusions, warranty, support conditions and payment terms.

Worked examples

See how the assumptions move the answer.

Published average only£3,500

The starting Great Britain average with no extra items or support entered. Replace it with a property-specific quote.

Quoted work outside scope£4,400

A £3,500 main quote plus £500 controls and £400 flue or condensate work entered separately.

Confirmed contributionSubtract it visibly

A documented supplier or scheme contribution reduces the entered budget, but the calculator does not establish eligibility.

Common questions

Questions homeowners ask before spending.

How much does a replacement gas boiler cost in the UK?

Energy Saving Trust currently gives £3,500 as the average cost of replacing a G-rated gas boiler with an A-rated boiler and thermostatic radiator valves in Great Britain. Your system type, location, pipework, flue, controls and other work can make a written quote materially different.

Does moving a boiler increase the replacement cost?

It can change gas and water pipework, electrical work, the flue and condensate route, access and making-good. This calculator does not invent a relocation percentage: enter the complete written quote and any separately priced work.

Who is allowed to replace a gas boiler?

Gas work must be carried out by an appropriately qualified Gas Safe registered engineer. Check the engineer and the relevant work categories directly with Gas Safe Register rather than relying only on an advert or logo.

Do I need a building-regulations certificate?

Replacement heating systems can be notifiable building work. A suitably registered competent-person installer can normally self-certify covered work and provide evidence of compliance; routes and requirements differ across UK nations, so confirm what applies before work starts.

Can I get help paying for a replacement boiler?

Some households may qualify for heating repair, replacement or wider efficiency work through ECO or a local route, but eligibility does not guarantee an installation. Enter support only after the responsible supplier, council or provider confirms it in writing.

Sources and review trail

Transparent inputs, versioned model.

Last reviewed: 13 September 2026
Model/version: uk-boiler-replacement-budget-2026.09.1

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