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What affects the cost of a combi boiler?
A combi boiler price depends on whether it is a like-for-like swap or a conversion from a tank system, how far the boiler moves, the flue, the gas pipe and the controls. This page does not print a price, because we could not find two dated public sources for one.
Last reviewed:What is in a combi boiler price?
A combi boiler heats water as you use it, so there is no hot water cylinder and usually no tanks in the loft. For a household in Cheshire weighing up a new one, the price is never only the boiler in its box. It is the boiler, the flue, any change to the gas and water pipes, the controls, the labour, taking the old boiler away, and the paperwork that registers the installation.
QuoteZila is starting in Cheshire, with Crewe, Nantwich and Sandbach among the first towns. Anyone in the UK can post a job or register a business. This guide does not print an installed price. We looked for two dated public sources for a combi boiler figure and did not find a pair that matched, so any number here would be a guess. What we can do is show which parts of the job move the total, so that you can ask engineers for quotes you can actually compare.
Swap, move or conversion?
The single biggest difference between two combi boiler quotes is usually the type of job, not the brand.
- Like-for-like swap. An old combi comes off the wall and a new one goes in the same place, using the same route for the flue. Pipework changes are small.
- Swap and move. The new boiler goes somewhere else, for example out of a kitchen cupboard and into a utility room or loft. New gas, water and condensate pipe runs follow, plus a new flue position.
- Conversion. The house has a regular or system boiler with a hot water cylinder, and often tanks in the loft. Converting to a combi means removing the cylinder and tanks, capping or rerouting old pipes, and checking the mains water supply can feed the new boiler.
Engineers price these as different jobs because they are. When you ask for quotes, say which one you want, or ask each engineer to say which they are quoting for. If one quote assumes a swap and another a move, the totals will not compare.
What changes a combi boiler quote
| What the engineer looks at | Why it changes the price | What to ask |
|---|---|---|
| Boiler model and output | Models differ in size, features and the warranty the maker offers | Which model and output, and why that one for your house |
| Flue route | A straight flue through an outside wall is simpler than a long or vertical flue | Where the flue will exit and whether extra lengths are included |
| Gas pipe size | A new combi may need a larger gas supply pipe from the meter | Whether the gas pipe has been checked and any upgrade is priced |
| Condensate pipe | The condensing boiler needs a drain route for its waste water | Where the condensate pipe will run, inside or out |
| Water pressure and flow | A combi relies on the mains for hot water | Whether they have tested flow at a tap and what they found |
| Cleaning the system | Old sludge can harm a new boiler | Whether a chemical clean or powerflush is included, and which |
| Filter and controls | Filters and controls are often separate lines | Which filter and controls are included |
| Old boiler and cylinder | Removal and disposal take time | Whether removal, disposal and making good are in the price |
| Carbon monoxide alarm | Approved Document J expects one in the room for a new or replacement fixed gas appliance, other than one used only for cooking [S4] | Whether one is supplied and fitted |
| Registration and paperwork | The installation must be signed off | How it will be registered and when you get the certificate |
A quote that leaves out a line is not automatically cheaper. It may mean that line is not included, or that it will be added later.
Who can fit a combi boiler?
Fitting a gas boiler is gas work. HSE says anyone employed to work on gas appliances in a home must be a Gas Safe registered engineer and competent in that area of work, and that the engineer's ID card lists their competencies on the back [S1]. Check the card on the day, and check the engineer on the Gas Safe Register before you agree a date.
There are no DIY steps in this guide. Do not take an old boiler off the wall, empty the system or move gas pipes to save on labour. If you smell gas at any point, call the gas emergency line and keep away from switches and flames.
Gas Safe Register. QuoteZila is not affiliated with this organisation.
Paperwork that should come with the job
A new boiler comes with more than a receipt. Ask about each of these before you agree:
- Building regulations. GOV.UK lists installing or replacing a heating system among work that may need building regulations approval, and says you do not need to arrange it yourself if the installer is registered with a competent person scheme [S2]. Ask how the engineer will register the work and when you will receive the certificate.
- The maker's warranty. Ask who registers the maker's warranty, and whether the maker sets conditions such as an annual service or a filter. Keep the paperwork.
- The first service date. HSE advises that gas appliances are serviced at least once a year by a Gas Safe registered engineer [S6]. Note the date the boiler was fitted.
- Instructions. Ask for the user manual and a quick walk-through of the controls before the engineer leaves.
Keep all of this together. You will want it if you sell the house or if something goes wrong.
Controls and efficiency
The Energy Saving Trust says a boiler-based central heating system should have at least a programmer, a room thermostat and thermostatic radiator valves [S3]. Some quotes include new controls as standard. Others assume your existing thermostat and valves stay. Neither is wrong, but the two quotes are not the same job.
If you are thinking about smart controls, ask how they work with the boiler model being quoted. If radiators are old, sticking or patchy, say so. A heating engineer may suggest cleaning or balancing the system at the same time, which can be simpler to arrange while they are already there than as a separate visit.
Is a combi right for my house?
A combi suits many homes, but not every one. Some questions an engineer may ask:
- How many bathrooms and showers are used at the same time?
- How strong is the water flow at the kitchen tap?
- Is there space for a hot water cylinder if you keep one?
- Do you have, or plan, solar panels or a heat pump?
If an engineer suggests keeping a cylinder or choosing a system boiler instead, ask them to explain why in writing. A good explanation is worth more than a lower price for the wrong boiler.
Timing, disruption and winter
A boiler swap means a period with no heating and no hot water. Ask each engineer how long they expect to be in the house, whether the job runs over more than one day, and what happens if a part is missing on the day. A conversion usually takes longer than a swap, because the cylinder, tanks and old pipes come out as well.
Think about timing. If the old boiler still works, you can choose a date that suits you rather than taking the first slot after a breakdown. If it has already failed, say so in your request, and say whether anyone in the house is elderly, unwell or very young, so the engineer understands the urgency.
Ask too about making good. Moving a boiler or a flue can leave holes in walls, cupboards and ceilings. Find out whether filling, sealing and decorating are included, or left for you to arrange.
Jobs you might post
These are examples, not taken from real job posts.
- "Old combi in the kitchen cupboard is fifteen years old and keeps losing pressure. Looking for a like-for-like replacement in the same place."
- "Want to convert from a system boiler and cylinder to a combi. Two-bedroom house, one bathroom."
- "Would like the boiler moved from the kitchen to the garage as part of a kitchen refit."
Include the age and make of your current boiler, where it is, whether you have a cylinder or tanks, and photos of the boiler, the flue and the gas meter.
How to compare combi boiler quotes
Citizens Advice says a quote is a fixed price and an estimate is only a guess, and suggests getting written quotes from at least three traders [S5]. For a boiler, ask each engineer to set out:
- The boiler make, model and output.
- Whether the job is a swap, a move or a conversion.
- The flue, gas pipe and condensate work included.
- Any system clean, filter and controls.
- Removal and disposal of old equipment.
- Whether VAT is included. A business must register for VAT when its taxable turnover goes over £90,000 [S7].
- How the installation will be registered, and when you get the certificate.
- The deposit asked for. Citizens Advice suggests not agreeing to more than 25% and always getting a receipt [S5].
When three quotes cover the same eight points, the comparison is fair.
Get quotes for a combi boiler
Describe the job, the boiler you have now and your postcode. QuoteZila is free for customers and local businesses [QZ1]. Up to five matched local businesses can send you a quote [QZ2].
Honest status: QuoteZila is new. We're starting in Cheshire, beginning with Crewe, Nantwich and Sandbach, and growing area by area. Anyone in the UK can still post a job or register a business. How fast you get quotes depends on how many local businesses have joined near you. Businesses can register and receive jobs straight away. We don't check insurance, qualifications or registrations, so please check these yourself before you hire.
Posting a job is not open yet
See heating engineers for who installs and services boilers, plumbers for other pipework, and the plumber cost guide for how trade prices are usually set out. Servicing is covered in our boiler service cost guide.
Questions about combi boiler prices
How much does a combi boiler cost to install?
This page does not print a figure. A like-for-like swap in the same place is a smaller job than converting a house with a hot water cylinder and tanks, and the boiler model, flue and controls move the total too. Ask for itemised written quotes for the same specification.
Who can fit a combi boiler?
Only a Gas Safe registered engineer. HSE says anyone employed to work on gas appliances in a home must be on the Gas Safe Register and competent in that area of work, and that their competencies are listed on the back of their ID card.
Does a new combi boiler need building regulations approval?
GOV.UK lists installing or replacing a heating system among work that may need approval, and says you do not need to arrange it yourself if the installer is registered with a competent person scheme. Ask the engineer how the installation will be registered.
Do I need new heating controls with a combi boiler?
The Energy Saving Trust says a central heating system with a boiler should have at least a programmer, a room thermostat and thermostatic radiator valves. Ask whether the quote includes these, or assumes your existing controls stay.
Will I need a carbon monoxide alarm?
Approved Document J says that where a new or replacement fixed gas appliance is installed, other than one used only for cooking, a carbon monoxide alarm should be provided in that room. Ask whether the alarm is in the price.
How much deposit should I pay for a new boiler?
Citizens Advice suggests pushing any deposit as low as you can, not agreeing to more than 25%, and always getting a receipt. Ask what the deposit pays for, such as ordering the boiler.
Does QuoteZila check the businesses?
No. We don't check insurance, qualifications or registrations, so please check these yourself before you hire. You can report a quote or a business from your job page.
This page is general information, not professional or legal advice. QuoteZila does not check Gas Safe, WaterSafe, NFRC, NICEIC or other registrations against the register on your behalf: look them up yourself.
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- Cost to Move a Boiler: What Changes the Price. What moves the price of relocating a boiler: distance, the flue, gas and condensate pipes, making good and certification. This guide prints no price.
- Fireplace Installation: What to Compare. What changes a fireplace installation quote: the appliance, the hearth, the flue, the sign-off and the alarm. This guide does not print a fitting figure.
Sources
- QZ1: QuoteZila product fact. QuoteZila home and jobs-for-tradesmen copy.
- QZ2: QuoteZila product fact. QuoteZila FAQ and app README.
- S1: Domestic gas: frequently asked questions, HSE. Accessed 2026-10-25. https://www.hse.gov.uk/gas/domestic/faqs.htm
- S2: Building regulations approval, GOV.UK. Accessed 2026-10-25. https://www.gov.uk/building-regulations-approval
- S3: Heating controls, Energy Saving Trust. Accessed 2026-10-25. https://energysavingtrust.org.uk/advice/thermostats-and-heating-controls/
- S4: Approved Document J: combustion appliances and fuel storage systems, 2022 edition, GOV.UK (DLUHC). Accessed 2026-10-25. https://assets.publishing.service.gov.uk/media/6336e58be90e0772dc9651a2/ADJ_2022.pdf
- S5: Before you get work done on your home, Citizens Advice. Accessed 2026-10-25. https://www.citizensadvice.org.uk/consumer/getting-home-improvements-done/before-you-get-building-work-done/
- S6: Gas safety: home owners, HSE. Accessed 2026-10-25. https://www.hse.gov.uk/gas/domestic/faqownerocc.htm
- S7: Register for VAT, GOV.UK. Accessed 2026-10-25. https://www.gov.uk/register-for-vat