Boiler replacement: choosing a type and getting a fixed quote
How to pick the right type of boiler for your home, which kind of job you are looking at, and how to get a fixed quote you can compare.
Replacing a boiler: the short version
Most UK boiler replacements fall into one of three jobs: swapping like for like, converting an older tank-fed system to a combi, or replacing a system or conventional boiler that runs a hot water cylinder. The work is usually done in one or two days by a Gas Safe registered engineer, who also registers the new boiler for Building Regulations. For typical fitted prices and what moves them, see our guide to boiler replacement cost.
Choosing combi, system or conventional
| Boiler type | Best for | Watch out for |
|---|---|---|
| Combi | One bathroom, good mains pressure, no space for a cylinder | Flow drops if two taps run at once |
| System | Two or more bathrooms, good mains pressure | Needs room for a hot water cylinder |
| Conventional | Weak mains pressure, older homes with tanks in the loft | Uses loft and airing cupboard space |
If you are unsure, keep what you have unless it is letting you down. Changing type adds pipework, time and cost. Our guide to combi vs system vs conventional boilers goes through the trade-offs in more detail, and what size boiler do I need? explains kW (kilowatts, how much heat a boiler can produce) in plain terms.
Which job is yours?
- Like for like. The same type of boiler in the same spot. This is the quickest job, usually one day.
- A change of type. A combi conversion removes the tanks and cylinder, so it takes longer and needs more pipework.
- An old back boiler. Back boiler removal means taking out the unit behind the fire and fitting a new boiler elsewhere.
- Off the gas grid. See oil boiler replacement.
Getting a quote you can compare
Ask each installer to name the boiler model, its kW output and the warranty length, and to list anything they have left out. Send the same photos and details to each one so the quotes line up. Before you book, check that the engineer is Gas Safe registered and read what happens on installation day.
If your home is well insulated and you plan to stay a while, it is worth reading about heat pump installation before you commit to another boiler.
Typical prices
| Job | Typical price | Fitting time |
|---|---|---|
| Combi to combi swap | £2,200 to £3,400 | 1 day |
| System or regular to combi | £3,000 to £4,200 | 1 to 2 days |
| System boiler replacement | £2,800 to £4,000 | 1 to 2 days |
| Boiler and full system flush | add £300 to £500 | same day |
Including VAT, checked October 2026. England prices shown; grants differ in Scotland, Wales and Northern Ireland.
Boiler replacement services
Guides
- Boiler replacement cost UK
- What size boiler do I need?
- Combi vs system vs conventional boilers
- How long does a boiler last?
- Signs your boiler needs replacing
- Boiler efficiency ratings explained
- Boiler warranties explained
- Hydrogen-ready boilers: are they worth it?
- Boiler finance and paying monthly
- What happens on boiler installation day
Boiler replacement by city
England
- Birmingham
- Bolton
- Bournemouth
- Bradford
- Brighton
- Bristol
- Cambridge
- Chelmsford
- Coventry
- Derby
- Doncaster
- Exeter
- Gloucester
- Huddersfield
- Hull
- Ipswich
- Leeds
- Leicester
- Liverpool
- London
- Luton
- Manchester
- Middlesbrough
- Milton Keynes
- Newcastle
- Northampton
- Norwich
- Nottingham
- Oxford
- Peterborough
- Plymouth
- Portsmouth
- Preston
- Reading
- Sheffield
- Southampton
- Stoke-on-Trent
- Sunderland
- Swindon
- Wakefield
- Warrington
- Wolverhampton
- York
Northern Ireland
Common questions
Which type of boiler should I get?
Usually the same type you have now, unless something about the house has changed. A combi suits one bathroom and good mains pressure. A system or conventional boiler suits homes where two showers run at once or the mains pressure is weak.
Does City Boiler fit the boiler?
No. City Boiler connects you with independent local installers who are Gas Safe registered. The installer gives you the fixed price, fits the boiler and registers it.
How long does a boiler replacement take?
A swap of the same type is usually one day. A conversion to a combi, or moving the boiler to a new position, usually takes one to two days.
Do I need a survey before I get a fixed quote?
For a like-for-like swap, many installers can quote from photos of the boiler, the flue and the gas meter. A change of type or a new boiler position usually needs a visit first. Either way, the quote should be fixed in writing before work starts.