What a new boiler costs in the UK
Most homeowners pay between £2,200 and £4,200 for a new gas boiler, fitted and including VAT. Where you land in that range depends mostly on the type of job, not the brand. A straight combi swap sits at the bottom. Changing the type of system, moving the boiler or replacing a cylinder pushes it up. All prices below are typical national ranges, checked October 2026.
| 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 |
Two jobs fall outside these bands. Back boiler removal usually costs more than a standard conversion, because of the fireplace work. An oil boiler replacement usually costs more than a gas combi swap, because the boilers are dearer and the job often includes oil line or tank work.
The extras that change the total
The headline price covers the boiler and a standard fit. These are the items that most often move it.
| Extra | Typical cost |
|---|---|
| Larger output boiler (for example 35kW instead of 24kW) | £150 to £400 more |
| New flue, or flue in a new position | £150 to £500 |
| Gas pipe upgrade to 22mm | £150 to £400 |
| Full power flush | £300 to £500 |
| Smart thermostat, fitted | £150 to £300 |
Not every job needs any of these. A combi going back in the same spot, with a sound flue and a clean system, may need none. A conversion in an older house might need three.
What pushes a price up
Changing the type of boiler
Moving from a conventional or system boiler to a combi means removing a cylinder and loft tanks, rerouting pipes and often upgrading the gas pipe. That is why a conversion costs more than a swap. Going the other way, from combi to system, means finding space for a cylinder and adding one, which costs more again.
Moving the boiler
Every metre the boiler moves means more gas, water and condensate pipe, and often a new flue route through an outside wall. If the current position works, keeping it is one of the easiest ways to save money.
The brand and the warranty
Boilers from the bigger brands with 10 or 12 year warranties tend to cost more to buy. A longer warranty is worth having, but read the conditions: most require an annual service by a Gas Safe engineer to stay valid.
The condition of your system
Sludge and magnetite (black iron oxide that builds up in radiators) shorten the life of a new boiler and can void the warranty. If the water that comes out of a radiator bleed valve is black, expect your installer to recommend a power flush.
Where you live
Labour costs vary around the UK. Prices in London and the South East tend to sit higher in the range than elsewhere, but the gap is mainly in labour, since the boilers cost the same.
What a fixed price should include
A fixed quote is only useful if you can see what it covers. Look for these items in writing:
- The boiler make, model and output in kW.
- The warranty length and the conditions attached to it.
- Removal and disposal of the old boiler, and any tanks or cylinder.
- A magnetic filter, and a chemical clean or power flush.
- The controls being fitted, such as a programmable or smart thermostat.
- Any flue, gas pipe or condensate work.
- Commissioning, Building Regulations notification through Gas Safe, and warranty registration.
If a quote does not name the boiler model, you cannot compare it with anything. Ask for it before you go further.
How to compare three quotes
Line the quotes up item by item using the list above. Differences usually come down to three things: a cheaper boiler with a shorter warranty, an extra like a flush left out, or a different view on whether the gas pipe needs upgrading. None of these are wrong in themselves, but you should know which you are choosing.
Ask each installer why they have specified what they have. A good one will explain, for example, why your 15mm gas pipe needs upsizing or why your system needs a flush. Then check the engineer’s Gas Safe number on the Gas Safe Register. City Boiler connects you with independent installers who are Gas Safe registered and gives you a fixed price before anyone starts.
Spreading the cost
If paying in one go is difficult, many installers offer monthly payments through a lender. Check the APR and the total repayable. Our guide to boiler finance and paying monthly covers what to look for.
Is a new boiler the cheapest option long term?
For most homes needing heat quickly, yes. A new combi is the lowest cost route to reliable heating and hot water. In a well-insulated home where you plan to stay for many years, it can be worth comparing the total cost of a heat pump after grants. Our heat pump installation page sets out those numbers.
Common questions
How much is a new boiler fitted in the UK?
A like-for-like combi swap typically costs £2,200 to £3,400 fitted, including VAT, checked October 2026. Converting to a combi is typically £3,000 to £4,200 and a system boiler replacement £2,800 to £4,000.
Why do boiler quotes vary so much?
Mostly because they cover different things. One quote may include a system flush, a gas pipe upgrade and a 10 year warranty while another leaves them out. Compare the boiler model, kW output, warranty length and extras line by line.
Is it cheaper to repair or replace an old boiler?
A single repair is almost always cheaper today. Once a boiler is over 12 years old and needs repeat repairs or hard to find parts, the money is usually better spent on a replacement.
Can I pay for a new boiler monthly?
Many installers offer finance, often through a third party lender. Check the interest rate and the total amount repayable, not just the monthly figure.
Is a cheaper boiler a false economy?
Not always. A budget boiler fitted well, with a filter and a clean system, often outlasts a premium boiler fitted badly. Installation quality and warranty length matter as much as the badge.