Boiler installation means removing an old or failed boiler and fitting a new one sized to the property, with the flue, controls and pipework brought up to current standards. In London, a typical combi replacement costs £1,800–£2,800 inc. VAT depending on model, flue and pipework. BritCertify installations start from £1,499, with Building Regulations compliance notified through Gas Safe Register.
How much does a new boiler cost in London?
Our boiler installations start from £1,499 inc. VAT, and a typical combi replacement in London costs £1,800–£2,800 depending on the model, the flue and the pipework. The final figure comes from a survey, because two homes with the same boiler can need very different amounts of work.
| Factor | Why it changes the price |
|---|---|
| Like-for-like or relocation | Moving the boiler means new gas, water, condensate and flue routes |
| Flue type and route | Vertical flues through a roof, extended flues and plume kits cost more than a short horizontal flue |
| Gas supply | Older gas pipework can be too small for a modern combi and may need upgrading from the meter |
| System conversion | Replacing a regular or system boiler with a combi means removing the cylinder and tanks and altering pipework |
| Condition of the system | Sludge-laden systems need cleaning before a new boiler is connected |
| Access | Upper-floor flats without lifts, loft installations and building management rules add time |
Every quote is itemised and fixed in writing before work starts, so you can see exactly what you are paying for.
Which type of boiler suits your home?
The right boiler depends on how much hot water you use at once, your mains water pressure and the space available. Matching the type and output to the home matters more than the badge on the front.
| Boiler type | How it works | Usually suits |
|---|---|---|
| Combi | Heats water directly from the mains on demand, with no cylinder or loft tanks | Flats and smaller houses with one bathroom and good mains flow |
| System | Heats a stored cylinder of hot water on a sealed heating system | Homes with two or more bathrooms used at the same time |
| Regular (heat-only) | Works with a cylinder plus cold water and expansion tanks in the loft | Older houses where keeping the existing layout avoids major pipework changes |
Before recommending a combi, we measure the incoming mains flow rate and pressure. Some upper-floor flats in older London blocks have weak mains supplies, and a combi in that situation gives disappointing showers however good the boiler is. We size the output to the property’s heating and hot water needs rather than copying the old boiler’s rating.
What is included in a boiler installation?
A complete installation covers far more than swapping one appliance for another:
- a survey of the gas supply, flue route, condensate route, water flow and electrical supply;
- removal of the old boiler and any redundant flue;
- a system clean and, where needed, a magnetic filter to protect the new heat exchanger;
- heating controls that meet Building Regulations requirements;
- commissioning, including gas rate and flue gas analysis, recorded on the Benchmark checklist;
- registration of the boiler with the manufacturer so the warranty is active;
- notification of the installation to Gas Safe Register for Building Regulations compliance.
Installing a gas boiler is notifiable under the Building Regulations. Because the work is carried out by a Gas Safe registered engineer, it is notified through Gas Safe Register, which then issues a Building Regulations Compliance Certificate to the property owner. Warranty terms vary by manufacturer and model, and we confirm them in your quote. Gas work is carried out by Gas Safe registered engineers (Gas Safe reg. 962998). Always ask to see the engineer’s Gas Safe ID card, or check registration on the Gas Safe Register website.
What London issues affect boiler installations?
Most complications on London jobs come from the building rather than the boiler.
- Leasehold flats: a new flue through an external wall usually affects the freeholder’s part of the building, so check your lease and get consent before agreeing a new position.
- Conservation areas and listed buildings: a flue on a front elevation may need planning permission or listed building consent. Check with your council early.
- Flue positions: terminals must keep set distances from windows, doors, boundaries and balconies. Narrow lightwells in Victorian conversions often need a plume kit or a different route.
- Loft installations: the loft needs a fixed ladder, boarding and lighting for safe installation and future servicing.
- Older properties: any building built or refurbished before 2000 may contain asbestos, sometimes in old flue pipes or boiler cupboard linings. If we suspect it, work stops until an asbestos survey confirms what is there.
How should you prepare for the installation?
- Clear the boiler cupboard and the route to it, including any loft hatch, and move valuables away from the work area.
- In flats, tell the managing agent in advance, as many blocks set working hours, lift protection rules or parking restrictions for contractors.
- If the property is let, agree the date with your tenants in writing and plan for a day without heating or hot water.
- Find any paperwork for the old system, such as previous service records, so the engineer knows its history.
What happens on installation day?
A like-for-like combi swap is usually completed in one day; conversions and relocations take longer. Heating and hot water are off while the system is drained, the old boiler removed and the new one fitted, and water and power are switched off for short periods.
Before leaving, the engineer commissions the boiler, completes the Benchmark checklist and shows you how to use the controls, read the pressure gauge and top up the system with the filling loop. The Building Regulations Compliance Certificate follows from Gas Safe Register after notification. Book an annual boiler service to keep the warranty valid. Landlords also need a current record for the property, so ask us to arrange the next gas safety certificate at the same time.
What if the survey finds a problem?
We tell you before you commit. Undersized gas pipework, a flue position that cannot comply, weak mains water flow or heavy sludge are either priced into the quote or flagged as decisions for you to make. If something hidden turns up during the work, such as corroded pipework under the floor, we stop, explain it and agree any extra cost before continuing.
For landlords, a new boiler can also help with energy efficiency targets. The government has confirmed that privately rented homes must reach EPC band C for all tenancies from 1 October 2030, with a landlord cost cap of £10,000 per property, or 10% of the property’s value if lower. Replacing an old boiler is one of the measures that can improve a rating, and our guide to EPC C by 2030 explains what the change means for London landlords.
Boiler installation prices in London (inc. VAT)
| Option | Price (inc. VAT) | Notes |
|---|---|---|
| Boiler installation or replacement | From £1,499 | Confirmed in writing after survey |
| Typical combi replacement in London | £1,800–£2,800 | Depends on model, flue and pipework |
Prices include VAT and are confirmed in a fixed written quote after survey. Central London parking or Congestion Charge may be added; we always confirm before booking.
Book this serviceWhat's included
- Home survey and fixed written quote
- Removal of the old boiler
- New boiler, flue and controls installed
- System clean and magnetic filter where needed
- Commissioning with flue gas analysis
- Benchmark checklist completed
- Manufacturer warranty registration
- Building Regulations compliance notified via Gas Safe Register
How it works
Survey
We check the gas supply, flue route, water flow, condensate route and controls, then recommend a boiler and send a fixed written quote.
Preparation
We agree the date, any freeholder or building management requirements, parking, and how long heating and hot water will be off.
Installation
A Gas Safe registered engineer removes the old boiler, fits the new one, cleans the system and connects the controls.
Commission and register
The boiler is commissioned, the Benchmark checklist completed, the warranty registered and Building Regulations compliance notified via Gas Safe.
Boiler Installation & Replacement: frequently asked questions
How much does a new combi boiler cost in London?
A typical combi replacement in London costs £1,800–£2,800 inc. VAT with BritCertify, depending on the boiler model, the flue and the pipework, and installations start from £1,499. Moving the boiler, upgrading the gas supply or converting from a cylinder system adds to the cost. Every price is confirmed in writing after a survey.
How long does a boiler installation take?
A like-for-like combi replacement in the same position is usually completed in one day. Relocating the boiler, converting from a system with a hot water cylinder, or running a new flue or gas supply generally takes longer. Heating and hot water are off while the work is carried out, so we agree timings with you in advance.
Do I need Building Regulations approval for a new boiler?
Installing a gas boiler is notifiable work, but you do not need to apply to building control yourself. A Gas Safe registered engineer notifies the installation through Gas Safe Register, which issues a Building Regulations Compliance Certificate to the property owner. Keep it with the boiler paperwork, because buyers' solicitors will ask for it when you sell.
Will you register the manufacturer's warranty?
Yes. We register the new boiler with the manufacturer after commissioning and complete the Benchmark checklist in the manual. Warranty length and conditions vary by manufacturer and model, so we confirm the terms in your quote. Most warranties require an annual service by a Gas Safe registered engineer to remain valid.
Can I swap my hot water cylinder system for a combi?
Often, yes, if the mains water supply has enough flow and pressure and the household does not need several showers running at once. Removing the cylinder and loft tanks frees up space, but a combi can only deliver so much hot water at a time. We measure your mains flow on survey before recommending it.
Can a new boiler be installed in a different location?
Usually, provided there is a compliant flue route, a suitable gas supply and a route for the condensate pipe. In London flats the flue position is often the deciding factor, because of the distances required from windows, doors and boundaries, and because leaseholders may need freeholder consent for a new opening in an external wall.
Sources and official guidance
Written and checked by the BritCertify technical team. Last reviewed 6 October 2026.