Learn all there is to know on combi boilers installation. The all-in-one blockbuster of a boiler which can heat your home up fast, but keep your bills down.
Combi boilers or combination boilers aren’t truly appreciated until something goes wrong, and when they do go wrong, boy, you'll know. Few things grab your attention like a cold shower.
If you are on the hunt for a new boiler replacement, you have probably encountered the various different types of boilers available.
Combi boilers are the most frequently installed in UK households, so if you live in an average-sized property, it’s likely the best choice for you. On the other hand, if you’re an orphaned wizard boy living under your uncle’s stairs, this article isn’t for you - but keep up your hopes that a hairy giant will soon come to get you.
Book before 3 pm and you could get your new combi boiler installed as quick as tomorrow. Check the latest boiler prices here.
Key points:
The final price of a combi boiler install depends on a variety of factors including the model e.g. premium or value, the overall complexity of the installation and whether you want to move your boiler.
For example, a straightforward combi swap is the most popular and typically the least expensive.
All new combi boiler quotes with Heatable include combi boiler installation, parts, labour and VAT.
You can pay for your new combi boiler in monthly instalments and with zero interest.
A 12-year boiler warranty is available for certain models.
Next-day boiler installation is available (subject to installer availability).
At Heatable, new combi boiler prices are fixed, so won't change, get your custom boiler quote here.
What is a combi boiler?
A combi or combination boiler is a type of boiler that provides both hot water and heating from a single, wall-hung unit.
This is in contrast to other types of boilers e.g., system and regular (heat-only) boilers that require separate hot water storage tanks, meaning they require much more space to house and take longer to install. If things being difficult and taking up too much space remind you of your mother-in-law, you got our point.
Simply put, they're fantastic and if you want one, get one.
Advantages of combi boilers
Modern combi boilers are the most popular choice when it comes to residential heating and hot water in the UK. Admittedly, it’s not the BAFTAs, but still an important popularity contest in life for normal folks.
Compact Design
They are supplied with water directly from the mains water supply, eliminating the need for large storage cylinders and tanks.
This means they are ideal for smaller properties or simply those that do not have the necessary space to house a separate cylinder. Or just people who have better use of their space than a big water tank.
Instantaneous Hot Water
Combi boilers provide hot water on-demand and almost instantly since water is fed to them from the mains and heated as it’s used.
In boilers that use a tank, you may have to wait for the tank of cold water to be reheated, which can be very inconvenient.
Imagine if Usain Bolt was your postman, but he also did your bins. A combi boiler is like that, basically.
Faster Install Time
Since most of their parts are mostly internal, it also means they are one of the quickest types of boilers to install, meaning that our engineers could have the boiler fitted the same day. And we love our engineers, but nobody wants them around for longer than necessary.
Clean & Safe
Since combi boilers get their cold water directly from the mains water supply, there is none stored in a tank which means there's a lesser risk of a leak.
How do combi boilers work?
Cold water is fed into the combi boiler directly from the mains water supply, the gas fuel is then burned to produce heat, which is transferred from the combustion chamber to the water via the heat exchanger.
...It's all very clever and complicated, honest.
When the temperature in your home drops, your thermostat (or, even better, smart thermostat) will detect this, send a signal to your combi boiler, and it will fire up to generate the required heat. It’s like someone refilling your coffee when you’re almost out.
Once the desired temperature has been achieved, the boiler will reduce its heat output and maintain the status quo, helping to reduce energy waste, while keeping your home warm.
If someone uses a hot tap, shower, or bath within the home, the diverter valve will direct hot water to the outlets while they are in use.
Once the tap is turned off, the diverter will be restored to the central heating position.
Hot water can be directed to the central heating or the water outlets, but never both simultaneously. Theoretically, you could take a long, steaming hot shower and find your shivering wife on the couch covered by a blanket.
The image above shows a Worcester Bosch 4000 installed by the Gas Safe engineers here at Heatable. Get your free quote from us here.
Who is a combi boiler not suitable for?
If you already have a combi boiler installed on your property, it’s likely that a replacement combi is exactly what you need - you can get a quote for a replacement combi boiler, here.
There are some circumstances in which a combi boiler may not be the most suitable type of boiler for your home.
If you've got a generously proportioned home with many, many bathrooms — avoid a combi like the plague. Go for a system boiler instead.
For example, if you have a larger property with multiple bathrooms/or a high hot water demand. As a rule of thumb, if your estate could be featured in a Jane Austen novel, a combi boiler isn’t for you.
Additionally, there are rare reasons, such as if you live in an area that suffers from a low mains water pressure.
How much will a new combi boiler cost?
The exact cost of a new combi boiler installation depends on a variety of different factors, these include the following:
The type of boiler installed e.g. a combi vs system vs regular
Brand and model of the boiler e.g. budget vs premium
If you are converting from one boiler type to another e.g. from a system to a combi
If you want to move the location of your boiler
Any extras e.g. radiators, smart controls etc
Adding unnecessary decorations to your boiler’s exterior
For an absolutely massive and excessively long guide, check out our new boiler costs bible. It has less violence or moral instruction but is also shorter than the real Bible.
However, for illustration purposes here's a quick guide to what our baseline costs currently are for different types of combi boiler installations:
Install Type | ~ £Cost |
Combi Boiler Replacement | £1,965 |
System/Regular Conversion | £2,545 |
Back Boiler Conversion | £2,795 |
To get a more accurate, up-to-date price for your home, head to https://heatable.co.uk/new-boilers
The type of boiler model you choose is also a factor and here at Heatable, we offer boilers for every budget, including the likes of premium, award-winning boiler brands such as Worcester Bosch and more budget-orientated (yet still very reputable) brands like Alpha.
The fixed price we offer includes the complete combi boiler installation, including the boiler itself and Gas Safe Installation from a registered engineer. If your engineer drinks coffee, you’ll have to provide it yourself.
If you want to read a more detailed guide and get an idea of the cost of some of the most common boiler installation scenarios, check out our complete guide to new boiler costs.
Combi boiler installation factors to consider
Getting a new combi boiler installed is by no means the cheapest thing you can do and since it’s likely going to be part of your home for the next decade, it’s important to consider some key factors before making a final decision. Combi boilers live as long as dogs, and you wouldn’t just pick any size dog, either, no matter how good they are at heating water.
These considerations include the following:
What size combi boiler do you need? (kW output)
A boiler's power is measured and provided in kilowatts(kW), so in the most basic terms, the greater the kW, the greater the boiler's ability to meet your home’s hot water and heating demands.
Important note, a boiler's size refers to its power output (kW) and not it's dimensions
The good thing is that most boiler manufacturers offer their boiler models in a wide variety of different sizes.
Our quick boiler tool can help you determine what size boiler you need in a matter of seconds.
The size boiler you require is largely determined by the number of radiators in your property, so by that logic, if you have a small property e.g., a flat, a small boiler will do the job.
However, if you live in a large property with multiple rooms and many radiators, you are going to need a powerful boiler to keep up with the high hot water demands. Likewise, if you have a large family and like your kids more or less clean, you’ll need a bigger boiler.
Here are some (rough) examples of recommended boiler kW outputs based on your home’s estimated demands:
No. of separate showers/baths | 2 Beds | 3 Beds | 4 Beds | 5 Beds |
1 Bathtub/Shower | ~26kW | ~29kW | ~29kW | ~35kW |
2 Bathtubs/Showers | ~29kW | ~35kW | ~35kW | ~35kW |
Where do you want your combi boiler located?
Do you want your new combi boiler installed in the same location as your current one? Or would you like to move it to a new location? Perhaps in an attic or in a kitchen cupboard? Perhaps under the stairs, although you’ll have to find a new spot for that orphaned wizard boy.
It’s possible to have your boiler moved to a different location, but you should be prepared to pay more, and it could take more time to install.
Moving a boiler’s location usually requires installing new pipework, and a new flue and it can also involve more mess.
This all results in higher labour costs and more materials, which can add costs to your combi boiler installation. The farther your boiler moves, the more costs will be involved, so we recommend at least keeping it on your property.
Combi boiler efficiency
All modern combi boilers use condensing technology, which makes them ultra-efficient, helping you to reduce your carbon footprint and save more money on your energy bills.
The good news is that all the combi boilers offered via Heatable are certified as A-rated, meaning they all have an efficiency rating of at least 90%. That’s a lot better than most politicians we know.
You can also purchase your boiler with the latest Google Nest Smart thermostat to reduce energy waste even further.
They're all A-rated, so you know they're good
How much exactly? Well, according to the Energy Saving Trust:
If you replace your old boiler with an A-rated boiler and set of heating controls (you can even operate it remotely via an app on your phone) you could save about £340 and 1,500kg of carbon dioxide a year. Those savings could buy you two new boilers after a decade - or something more fun instead.
How long does a combi boiler installation take?
This is a very important question, because you may need to take a day or two off work. There goes your £340 in savings.
The answer is that it depends on the type of installation, as some will be more complex and take a longer time than others.
Installation Type | Time |
Boiler swap | 1 day |
Boiler swap with relocation | 1-2 days |
Conversion from regular to combi | 2 days |
BBU conversion to combi | 2 days |
Combi boiler brands - which are the best?
Here at Heatable, we offer a variety of different boilers from various manufacturers to suit any budget, all of which are award-winning and have impeccable reputations (just check their Trustpilot).
These are the boiler brands you can buy with us:
Worcester Bosch combi boilers
Worcester Bosch is a household name in the world of British boilers and holds a royal warrant.
They are the only brand to have held a Which? Best Buy Award for over a decade, so they are clearly doing something brilliant.
Combine their awards with their reputation for excellent customer service and aftercare, an unbeatable guarantee, as well as easily sourced parts and you have the best boiler brand in the UK. These credentials do all the talking, but we’ll translate for you.
To get a fixed price on a new Worcester Bosch boiler, click here.
Viessmann combi boilers
Viessmann is a relatively new name in the British boiler scene, but they have dominated the European market for decades, so they are by no means a new manufacturer.
Their German engineering and crisp, innovative designs make them hard to beat, combine that with their awards and a 5-star reputation and it’s a boiler brand you can put your trust in. You get used to their accent pretty quickly.
To get a fixed price on a new Viessmann boiler, click here.
Alpha combi boilers
Alpha boilers are a superb option for anyone looking for a budget-friendly alternative to the bigger brands (and who isn't), but with equity when it comes to technical brilliance.
Made in Italy and headquartered in Kent, they are a fantastic option for the buyer who is looking for a reliable and affordable heating solution with an incredible warranty (10 years exclusive to Heatable).
To get a fixed price on a new Alpha boiler, click here.
Combi boiler installation finance
If you don’t have all the money for a new boiler upfront or would simply like to spread the cost and pay monthly, you can thanks to our boiler finance options.
If you meet the lender's eligibility criteria, you can potentially pay for your boiler in monthly instalments over 3, 5, 7 or 10 years.
Pay monthly boiler replacement finance summary:
No deposit is required (up to 50% optional).
Make overpayments with no penalty.
Spread the cost over 3, 5, 7 or 10 years.
Interest rates from 9.9% APR.
Get a quote for your new combi boiler installation
If you’re aiming to get the best deal on a new boiler, consider getting a quote from us, here’s why:
Gas Safe installation within 24 hours.
Thousands of satisfied customers with an average score of 4.9 on Trustpilot, surpassing the market leader.
Which? Trusted Trader: Heatable is proudly recognised as a Which? Trusted Trader.
Price match guarantee: We will match any like-for-like cheaper quote.
Flexible payment options, including interest-free finance*.
Up to 12-year guarantee on selected boilers.
Fixed price guarantee: No hidden costs.
Save your quote and decide later.
Get an instant fixed price on a new boiler, here.
To learn more about boilers, visit our advice section, check out our YouTube channel, or read customer testimonials here.
Heat Happy.
*finance is subject to status and affordability. Terms and conditions apply. Minimum payment terms apply.
