What a new boiler costs in London
Our published price for boiler installation starts at £700 + VAT. That figure comes straight from our price list, where it sits under plumbing and heating as a typical starting point. All our prices exclude VAT, so the VAT is added on top.
Nobody can give an honest final figure for a boiler without seeing what is there now. The boiler model, where it sits, the flue route, the gas pipe, the condensate and the state of the heating system all move the number. So we start from a photo, ask the few questions that matter, and send a fixed, itemised quote. The quote lists the boiler, the parts and the labour, so you can see exactly what you are paying for before you agree to anything.
What is included, and what is not
A standard like-for-like replacement, where the new boiler goes in the same place and uses a similar flue route, normally covers:
- Safely disconnecting and removing the old boiler
- Fitting the new boiler and connecting it to the gas, water and heating pipework
- Fitting the flue and connecting the condensate pipe
- Commissioning: testing the gas supply, setting the boiler up and checking it burns correctly
- Completing the manufacturer's Benchmark checklist with you
- Notifying the work under Building Regulations through Gas Safe Register
What usually sits outside a straight swap, and is quoted after a photo or a survey rather than guessed at here:
- Moving the boiler to a different room or wall
- A new flue route, or a flue that needs extensions or a plume kit
- Upgrading the gas pipe if the new boiler needs a larger supply
- Removing a hot water cylinder or tank when changing to a combi
- New radiators, valves or heating controls
- Cleaning a heating system full of sludge before the new boiler goes on
- Making good plaster, boxing or decoration after the work
We do not publish separate prices for these extras, because they depend entirely on the flat. They appear as separate lines in your quote, so nothing is added on the day.
How the job works, step by step
1. Send a photo
Send a photo of the boiler, the data plate if you can reach it, and the flue where it leaves the wall or ceiling. WhatsApp works, or attach photos to the quote form, or send them to Ayda, our assistant, in the chat on this page. Tell us whether it is a flat or a house, how many bathrooms you have, and whether you rent or own.
2. Fixed quote
From the photos we can usually tell whether the job is a simple swap or something larger. If it is clear, we send a fixed quote. If it is not, for example where the flue disappears into a ceiling void, an engineer visits to check before we quote. Either way you get the figure in writing before work starts.
3. Installation
A Gas Safe registered engineer removes the old boiler and fits the new one. In a flat we plan access first: porter booking, service lift, working hours and where materials will be kept. In many Central London blocks this is the difference between a smooth day and a lost one.
4. Commissioning and the Benchmark checklist
Once the boiler is in, the engineer commissions it: checks the gas pressure and flow, the combustion, the flue and the safety devices, and sets it up for your system. Every new gas boiler comes with a Benchmark commissioning checklist, usually in the back of the manual. The engineer fills it in and signs it. Keep it with the manual, because manufacturers usually ask for it if you ever claim under the boiler's warranty, and the engineer who services the boiler later will want to see it.
5. Building Regulations notification
Fitting a new gas boiler is notifiable work under the Building Regulations. A Gas Safe registered business can self-certify it, and Gas Safe Register then notifies the local authority. You receive a Building Regulations compliance certificate in the post. Keep it, because buyers' solicitors ask for it when you sell the flat.
Combi, system or regular boiler?
Most Central London flats suit a combi boiler. It heats water on demand, needs no hot water cylinder, and frees up the airing cupboard. The catch is that a combi depends on the incoming mains water. If the pressure or flow is weak, which is common on upper floors of older blocks, two taps running at once will feel it. We check the flow before recommending one.
A system boiler with a cylinder suits larger flats and houses with more than one bathroom in use at the same time. A regular boiler with tanks in the loft is usually only kept where the house is already set up for it. Changing from one type to another is a bigger job than a like-for-like swap, and your quote will say so.
Boilers in flats and mansion blocks
The flue
The flue is the part that most often decides the job. In purpose-built and mansion block flats, boilers often sit in internal kitchens or cupboards, with the flue running through a ceiling void to reach an outside wall. That route must be inspectable, which normally means hatches along it. A new flue terminal also has to meet clearance rules from windows, doors and boundaries, so it cannot always go where the old one was. Our gas safety certificate guide explains why flues in voids catch out so many landlords.
Freeholder consent
If the work changes the outside of the building or the structure, such as a new hole for a flue or a new condensate route, your lease will probably require the freeholder's or managing agent's consent first. Our guide to licence to alter in a mansion block covers how that works. Front elevations in conservation areas can bring their own rules on visible flues.
The condensate pipe
Every modern condensing boiler produces acidic water that must drain away safely. In a flat the condensate pipe usually runs to a kitchen waste or an internal stack. Pipes run outside can freeze in cold weather and shut the boiler down, so we prefer an internal route wherever the flat allows it.
Access and working hours
Mansion blocks in St John's Wood, Maida Vale and Marylebone usually require contractors to sign in, use the service entrance and work set hours. Our guide to porter access for mansion block works explains what to arrange in advance.
Is it time to replace, or just repair?
A new boiler is a big decision, and it is not always the right one. If you have no hot water, start with our guide to a boiler not heating water. If the pressure keeps dropping, read boiler losing pressure first. Both explain what you can safely check yourself and when a Gas Safe engineer is needed. Replacement usually makes sense when parts are no longer available, faults keep coming back, or the boiler has been condemned at a safety check.
For landlords
If you let the flat, the new boiler joins the annual gas safety check. A gas safety certificate is £85 + VAT, and the electrical side is covered by an EICR for landlords. Fitting a boiler between tenancies, rather than in the first cold week of winter, saves a tenant without heating and a rushed job.
Areas we cover
For leaks, taps, toilets and other heating and water jobs, see our plumbing service, with call-outs from £80 + VAT.
This is practical guidance rather than legal advice. Lease terms and local rules differ between buildings, so confirm what applies to yours before work starts.