Combi boiler installation · Fixed prices · Checked November 2026
A fixed online price, a Gas Safe engineer and everything you need included. Answer a few questions, pick your combi and choose your install date, often as soon as the next day.
4.6 on Trustpilot · 655 reviews (November 2026)- ✔ Over 15,000 boilers installed
- ✔ Fixed prices including VAT
- ✔ Gas Safe installation
Your old boiler has given up, or you’ve been told it’s time for a combi. Either way you want three things: a price you can trust, a proper installation and a date. This page shows our fixed combi installation costs model by model, exactly what’s included and whether a combi suits your home, so you can book with confidence.
How much does combi boiler installation cost?
Quick answer
Combi boiler installation with Eco Happy costs from £1,928.99 fitted including VAT for a like-for-like swap, and most of our combis cost £1,928.99 to £3,140. Converting a system or regular boiler to a combi adds £700, and replacing a back boiler adds £1,610. Your online quote fixes the price for your home.
Get your fixed combi quote
Tell us about your home
Answer a few quick questions, like how many bedrooms and bathrooms you have and what boiler you have now. It takes about 30 seconds to start.
Pick your combi
Choose from Viessmann, Worcester Bosch, Alpha and Ideal combis, add any extras and see monthly payments if you want to spread the cost.
Choose your date
See your fixed price including VAT and pick an install date. Installs are often available as soon as the next day; see live dates in your quote.
Combi boiler installation cost by type of job
The type of job matters more than anything else. A straight swap is the simplest and cheapest job, while a conversion means removing tanks or a cylinder and re-piping for the new boiler.
| Type of job | Eco Happy fixed price (inc. VAT) | Typical time |
|---|---|---|
| Like-for-like combi swap | From £1,928.99 (range £1,928.99 – £3,140) | 4–6 hours, done in a day |
| System or regular boiler → combi | From about £2,629 (your combi + £700) | Around 2 days (system), up to 3 days (regular) |
| Back boiler → combi | From about £3,539 (your combi + £1,610) | Longer than a standard swap |
| Moving the boiler (with any of the above) | Kitchen to airing cupboard £0 · same room £400 · another room £650 · cellar £650 · loft £950 | Adds pipework time |
What a combi installation costs by type of job (from-prices, inc. VAT)
Extras that can change the price
- Vertical flue through the roof: +£400 for the vertical flue kit.
- Extra flue parts beyond the standard package: flue extensions £100 per metre, bends £75 each, plume kit £100.
- Longer gas runs: 22mm gas pipe beyond the included allowance (5m on swaps, 10m on conversions) is £40 per metre.
- Smart controls: wireless controls are included, or upgrade to Google Nest or Hive (£219), Salus (£129) or a T6 smart thermostat (£199).
- Saturday installation: +£50.
- Not included: asbestos removal, scaffolding and specialist access equipment.
Comparing system and regular boilers too? See our new boiler cost guide. For what drives combi prices in general, read our combi boiler cost guide.
Combi boiler prices by model, fitted
| Combi boiler | Fixed price fitted (inc. VAT) | Manufacturer warranty |
|---|---|---|
| Viessmann Vitodens 025 28kW | £1,928.99 | 7 years |
| Alpha E-Tec NX 28kW | £2,015 | 12 years |
| Worcester Bosch Greenstar 2000 30kW | £2,250 | 8 years |
| Viessmann Vitodens 050-W 25kW | £2,400 | 12 years |
| Ideal Logic Plus C24 | £2,445 | 10 years |
| Worcester Bosch Greenstar 4000 25kW | £2,474.96 | 12 years |
| Worcester Bosch Greenstar CDi Compact 28kW | £2,540 | 12 years |
| Viessmann Vitodens 100-W 30kW (Beat the Bills) | £2,900 | 14 years |
| Worcester Bosch Greenstar CDi Compact 36kW | £3,140 | 12 years |
What’s included in every combi installation
Our prices are fixed and include VAT. Every Eco Happy combi installation includes:
- Removal, safe disposal and recycling of your old boiler
- Your new combi boiler and the flue it needs
- Pipework alterations and fixings to Building Regulations
- Chemical flush of your pipework and radiators
- Chemical inhibitor and a magnetic system filter
- Fixed materials pack
- Wireless heating controls (upgrade to smart at checkout)
- Rebalancing of your whole heating system
- New or upgraded condensate pipe if needed
- Gas pipe upgrade if needed, within the included allowance
- Any required electrical work
- Required external brickwork, including bricking up
- Installation by a Gas Safe registered engineer
- CP1 certificate, Building Control notification and warranty registration
- Manufacturer warranty plus our 12-month workmanship warranty
- Access to our customer support line
Is a combi right for your home?
A combi heats your hot water straight from the mains when you turn on a tap, so there’s no hot water cylinder or cold water tank. That makes it a great fit for many homes, but not all of them.
A combi is usually a good fit if…
You have one main bathroom (or a bathroom and an en-suite that aren’t used at the same time).
Your mains water pressure and flow are decent.
You’d like to free up the airing cupboard or loft space.
Consider a system or regular boiler if…
Several showers or baths often run at the same time.
Your mains pressure is low.
You want to keep a cylinder, for example for solar hot water.
Still not sure? Our guide to what type of boiler you need walks you through it, and the questions in our online quote check this for you before you buy.
Brands we install
We fit combis from Viessmann, Worcester Bosch, Alpha and Ideal. Manufacturer warranties on our combis run from 7 to 14 years depending on the model.
Your warranty cover
- Manufacturer warranty: 7–14 years of parts and labour, depending on your boiler.
- 12-month workmanship warranty, direct with Eco Happy.
- Exclusive Eco Happy warranty: two further years of parts and labour after the manufacturer warranty ends, as long as your boiler is serviced every year through Eco Happy.
Booking and installation day
Pick your date in the online quote, often as soon as the next day. A like-for-like combi swap is usually done in a day, and conversions take longer. Our guide to what happens on combi installation day covers the timings, the steps and what to check before your engineer leaves.
If your home isn’t what was ordered
If our engineer finds the job is different from the order (for example, a “combi swap” that has tanks in the loft), we’ll give you a corrected quote before any extra work goes ahead.
Ways to pay
Pay the fixed price in full at checkout, or spread the cost.
Want to compare installers first? See our guide to the best boiler installers and BOXT alternatives.
What our customers say
★★★★★
“Amazing work by Eco Happy, convert my old boiler to a combi boiler, quote me a very competitive price and done the job in 1.5 days… left everything nice and tidy.”
Mr Sergio Gomes, combi conversion · Trustpilot, Aug 2026
★★★★★
“Call Centre kept us on the right track and even advised us that we were asking for the wrong boiler type to meet our needs. We have just had a better boiler installed today for an excellent price!”
“Eco Happy boiler replacement” · Trustpilot, Oct 2026
Rated 4.6 out of 5 from 655 reviews on Trustpilot (November 2026). Read all reviews, good and bad →
Combi boiler installation FAQs
How much does combi boiler installation cost?
Our fixed fitted combi prices start from £1,928.99 including VAT (Viessmann Vitodens 025 28kW), and most of our combis cost between £1,928.99 and £3,140 for a like-for-like swap. Converting from a system or regular boiler adds £700, and from a back boiler adds £1,610.
Can you convert my system or regular boiler to a combi?
Yes, in most homes. Switching from a system or regular boiler to a combi adds £700 to the price of your chosen combi, and the engineer removes the old cylinder and tanks and re-pipes for the new boiler. Check a combi suits your hot water needs first.
Is the combi price fixed?
Yes. The price in your online quote is fixed and includes VAT. If our engineer finds your home is different from what was ordered, for example tanks in the loft on a combi swap, we give you a corrected quote before any extra work goes ahead.
How soon can you fit a new combi?
Installs are often available as soon as the next day. Your online quote shows live install dates for your postcode before you book.
Which combi brands do you fit?
We fit combis from Viessmann, Worcester Bosch, Alpha and Ideal, with manufacturer warranties of 7 to 14 years depending on the model.
How much does it cost to move a combi boiler?
Moving the boiler from the kitchen to the airing cupboard is £0, within the same room £400, to another room or the cellar £650 and into the loft £950, on top of your fixed combi price.
Are your engineers Gas Safe registered?
Yes. All gas work must legally be carried out by a Gas Safe registered engineer, and every Eco Happy installation is.
What warranty comes with a combi installation?
You get the manufacturer warranty (7 to 14 years depending on your boiler), our 12-month workmanship warranty and, if your boiler is serviced every year through Eco Happy, two further years of parts and labour after the manufacturer warranty ends.
Book your combi installation
Get a fixed price for your home in minutes, with everything included and a Gas Safe engineer to fit it, often as soon as the next day.
Prefer to talk? Call us on 0114 387 7066.
Eco Happy Installs Limited (FRN 1051640) is a credit broker working with a panel of lenders. We are authorised and regulated by the Financial Conduct Authority as a credit broker, not a lender. The availability of finance and the terms offered will depend on your individual circumstances. Credit is subject to status, affordability and lender approval. Terms and conditions apply.
