New Boiler Cost & Replacement Guide 2026
A new boiler costs between £1,500 and £3,500 installed for most UK homes. Whether you need a combi boiler replacement or you're switching from an old heat-only system, this guide walks you through what the job involves, how to find a Gas Safe registered engineer, and what to look out for in quotes so you don't overpay.
Must be installed by a Gas Safe registered engineer - it is a legal requirement. Working on gas appliances without Gas Safe registration is a criminal offence. Always check your engineer's card at gassaferegister.co.uk before any work begins.
Quick answer
How much does a new boiler cost?
Most UK homeowners pay between £1,500 and £3,500 for a new combi boiler, fully installed. A basic like-for-like swap with a budget boiler sits around £1,800; a premium Worcester Bosch or Vaillant with a 10-year warranty runs closer to £3,000–£3,500. For a full breakdown by boiler type and region, see our cost guide.
View the full boiler cost guideWhat does a boiler replacement involve?
A standard boiler replacement is usually a one-day job. The engineer removes your old boiler, fits the new one in the same position, connects it to the existing pipework, fits a new flue if needed, and commissions the system. Here is what happens on the day:
The gas supply is isolated and the old boiler is disconnected and removed
The new boiler is fitted and connected to your existing pipework, controls, and flue
The system is commissioned, pressure-tested, and the engineer completes the Benchmark certificate
You register the boiler warranty with the manufacturer - this step is easy to forget, so do it the same day
Things to think about before you hire
Combi, system, or heat-only?
A combi is right for most flats and smaller houses with one bathroom - it heats water on demand and removes the need for a cylinder. A system boiler suits homes with two or more bathrooms. A heat-only (conventional) boiler only makes sense if you already have a suitable hot water cylinder and cold water tank and do not want to change the setup.
Boiler brand and warranty length
Worcester Bosch and Vaillant tend to come with the longest manufacturer warranties (8–12 years on most models). Budget brands like Baxi and Ideal are not bad boilers, but their warranties are shorter - typically 2–5 years - and their failure rates over 10 years are higher. The extra £400–£600 for a premium brand often pays for itself in avoided repairs.
Magnetic filter and system flush
A magnetic filter fitted to the return pipe traps metallic debris before it reaches the boiler. Most manufacturers now require one to validate the warranty. If your heating system has not been flushed in years, ask for a power flush before the new boiler goes in - sludge from old pipework is one of the most common causes of new boiler failure.
Time of year
Heating engineers are busiest from October to January. If your boiler is limping along rather than failing outright, book a replacement in spring or summer. You will have more choice of engineer, more time to get three quotes, and potentially a better price - especially for labour.
How to find a good heating engineer
Check Gas Safe registration first
Before anything else, confirm the engineer is registered at gassaferegister.co.uk. Enter their registration number or name - takes 30 seconds. An unregistered engineer working on gas is breaking the law, and any work they carry out will not be certified.
Get at least three quotes
Prices for the same boiler can vary by £500 or more between engineers in the same postcode. Use a comparison service or ask neighbours for recommendations, then get written quotes from at least three engineers before deciding. Make sure each quote specifies the boiler model, flue type, and what is and is not included.
Check the warranty is included
Some quotes include registration of the manufacturer warranty; others do not. Ask specifically. A 10-year Worcester Bosch warranty is only activated if a registered Worcester Bosch Accredited Installer completes the job - a cheaper, non-accredited engineer may still fit the boiler correctly but you will only receive a 5-year warranty instead.
Ask about the magnetic filter
Any engineer who does not mention a magnetic filter as part of a new installation is cutting corners. It costs around £80–£120 fitted and is a warranty requirement for most brands. If a quote does not include one, ask why.
Read recent reviews carefully
Look for reviews that mention the engineer turning up on time, completing the work in one day, leaving the area clean, and explaining the controls before leaving. Those details tell you as much as the star rating.
Boiler guides
Boiler cost calculator
New boiler cost guide
Central heating cost guide
Power flush: what it costs and when you need it
Boiler service cost
Boiler Upgrade Scheme (BUS)
ECO4 Scheme: Free Boilers
Combi vs System Boiler
Oil Boiler Cost
Electric Boiler Cost
LPG Boiler Cost
Biomass Boiler Cost
Back Boiler Replacement
Best Boiler Brands 2026: Worcester, Vaillant, Baxi & More
New boiler FAQs
How long does a boiler replacement take?
A straight swap - same boiler type, same location - takes most engineers a full day. If you're changing boiler type (say, from a heat-only to a combi) or moving it to a different wall, expect two days, possibly three. Some jobs need new pipework or a flue relocation, which adds time.
Do I need to be in the house during the installation?
Yes. Your engineer will need access to your gas supply, electrical connections, and possibly the loft or airing cupboard depending on your system. You'll also need to sign off the Benchmark Commissioning Certificate at the end, which activates your boiler warranty.
Will I be without heating and hot water during the job?
For most of the day, yes. A single-day swap usually means your heating is off from morning until mid-afternoon. It's worth planning for this - especially in winter. If your old boiler fails in an emergency, many engineers will prioritise you, though rates may be higher.
What happens to my old boiler?
A reputable engineer will remove and dispose of your old boiler as part of the job. Gas appliances are classed as controlled waste and need to be disposed of correctly. Always confirm removal and disposal is included in your quote before signing anything.
How do I know if an engineer is properly Gas Safe registered?
Every Gas Safe registered engineer carries an ID card with their registration number and the types of work they are licensed to carry out. You can check any engineer's card at gassaferegister.co.uk. Ask to see it before work starts - any legitimate engineer will expect you to ask.
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