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Best Combi Boilers in 2021: Best Boilers to Buy (and avoid)

What is the best combi boiler? It's the burning question on the UK's lips. Here, we'll tell you what to look for and what to avoid when buying a new combi boiler for your home in 2021.

You might not have even been aware of your boiler until it failed you. It was a seldom thought of white box in the corner of an equally seldom thought of cupboard in a lesser used room. Going about its job in peace with a resolute and unfailing work ethic despite knowing full well you not only don’t care for it but prefer to pretend it doesn’t exist like Quasimodo, isolated to his cathedral.

But your home is your boilers Esmeralda and he’ll do anything to protect it, eventually proving his worth to everyone and hailed a hero. Well. At least a new gas combi boiler will.

Everyone has a passing knowledge of cars – just enough to make an informed purchase. But, what makes a new boiler the best? A brand name? Boiler size? Efficiency percentage? Awards?....Boiler awards exist?!

Our early spoiler has already let you in on our winner:  Worcester Bosch boilers. But there’s more to it than that, and much more boilers than that, including tough competition from the likes of Viessmann, Vaillant, BAXI, and more.

PS we fit new combi boilers with gas safe installation nationwide and as quick as tomorrow. Check the latest prices. 

Central Heating Combi Boilers

Best Combi Boilers of 2021 (By Brand)

To determine which are the best boilers available in 2021, we considered the following factors: 

  • Warranty period offered by the brand 
  • The overall reputation of the brand based on customer reviews 
  • Trustpilot reviews  
  • Awards and accolades e.g. Which? Best Buy Awards
  • Customer service performance 
  • The price range of their boilers  
  • Efficiency ratings 


A loveable list to start, here are our top 5 best combi boiler brands in the UK right now, in 2021:

  • #1 Worcester Bosch Combi Boilers
  • #2 Viessmann Combi Boilers
  • #3 Vaillant Combi Boilers
  • #4 Ideal Combi Boilers
  • #5 BAXI Combi Boilers

#1 Worcester Bosch Combi Boilers (Best boilers)

Worcester Bosch Boiler prices

A prestigious name within the heating industry and probably the UK’s best, most sought after combi boiler, historically. One of three combi boilers with the Which? Best Buy award and you can’t go far wrong with a Worcester.

Why do we think Worcester offers the best combi boilers? 

  • Which? Best Buy Award for 10-years running 
  • 10-year guarantee (when purchased via Heatable)
  • Availability of parts is second to none 
  • Excellent customer reviews and aftercare 

Want a new Which? Best Buy boiler with professional installation?

You can see the latest price on Worcester Bosch boilers here. 

Worcester 2021 combi boiler range & overviews:

Worcester Model Kilowatt (kW) outputs
Worcester Bosch Greenstar i - - 25kW 30kW
Worcester Bosch Greenstar 4000 - - 25kW 30kW
Worcester Bosch Greenstar Si Compact - - 25kW 30kW
Worcester Bosch CDi Classic 29kW 34kW 38kW

Worcester Bosch CDi Compact - 28kW 32kW 36kW
Worcester Bosch CDi Highflow - - 44kW 55kW

Worcester Bosch 2000 Style 24kW - - 30kW
Worcester Bosch 8000 Style 30kW 35kW 40kW 45kW

Need to know the cost of a new boiler, quick? Find out what replacement you need along with costs (takes 60 seconds).

Greenstar 4000 Combi Boiler (Replacing the Greenstar i)

Worcester Bosch Greenstar 4000 Combi BoilerThe Greenstar 4000 is a brand new arrival to the Worcester Bosch range of combi boilers, designed to replace the best selling Greenstar i range. The Worcester Bosch 4000 offers everything the i range did, but with some major improvements, including a quieter operation and a higher hot water output. 

The 4000 benefits from a new, sleek curved edge case, user-friendly digital display and easy to use push control buttons, a major improvement on the boring square boxes of old. 

Greenstar i Combi Boiler (Best combi boiler in terms of sales)

The Greenstar 30i is Worcester’s best seller and over a million of them are in homes throughout the UK. If choosing between the two, then do consider opting for the Greenstar 30i over the Greenstar 25i as they are known to be much more reliable and often don't have too much disparity in price. If you do have a super small property though, then the 25i will be more than adequate and could secure you a hell of a Worcester bargain.

Greenstar Si Compact Combi Boiler

Very similar to its namesake, the Greenstar Si boasts almost identical statistics and features and again is suitable for small to medium homes with one bathroom but a smaller frame allows this model to nestle into a kitchen cupboard – it's probably the best option if you require your combi boiler to be out of sight.

Check the latest deals on Worcester Bosch boilers here

CDi Classic Combi Boiler

A truly premium boiler from Worcester and their top of the line offering, in their opinion, it's probably the best combi boiler in their range. If you have your heart set on a Worcester then this is certainly one model to consider, although it may come with a more premium price tag.

Have you had a boiler quote yet? Use our calculator to get an instant new boiler quote. 

CDi Compact Combi Boiler

Another range topper from Worcester Bosch boilers with more compact dimensions for homes short on space. The CDi compact is still complete with outstanding efficiency levels, a Which? Best Buy award and can still pack a punch for its size – comfortably powering homes with two bathrooms.

Worcester Greenstar CDi Compact Price

Read our in-depth Worcester Bosch Greenstar CDi Compact Review.

CDi Highflow Combi Boiler

A monstrous floor standing combi boiler with industry leading hot water flow rates. Perfect for large homes with multiple bathrooms that don’t want to make way for an additional water tank. It's the best combi boiler for massive homes, not many can match its credentials.

Worcester Bosch 8000 Style

Worcester's most powerful and connected wall-hung boiler to date, capable of delivering up to 50kW's, and with optional smart technology that will top up the boiler for you when low pressure is detected. As its name suggests, it is also arguably the best looking boiler on the market and readily available in black - a boiler industry innovation on a par with the introduction of the iPod.

Read our in-depth reviews of some of the most popular models from the brand: 

Learn all about combi boilers in our what is a combi boiler guide and see how the brand fared against Baxi in our Worcester Bosch vs Baxi comparison. 

Worcester the way? We think so.

Worcester Bosch boilers are without a doubt one of the most reliable combi boiler brands and you can bag yourself a 10-year warranty (assuming you buy from a Worcester Approved Installer and not a rogue in an unmarked white van) giving you peace of mind no matter what.

Check the latest price on a Worcester boiler here

Worcester Bosch Guarantee

If you purchase a new Worcester Bosch boiler via Heatable, you will indeed secure yourself a lengthy 10-year guarantee. 

If you’re hellbent on getting a Worcester and quality is your top priority, you may want to consider exploration beyond the Greenstar i range - where Worcester's real quality lies - the 8000 Style is a great place to start. However, unlike other manufacturers, irrespective of your chosen Worcester Bosch model - you can always bank on Worcester's outstanding aftercare which is without a doubt, industry-leading.

You can check the latest deals on Worcester Bosch boilers here, and see how the brand compared to another market leader in our Worcester Bosch vs Vaillant Boilers post. 

They're award-winning boilers: Voted Which? Best Buy for 10 consecutive years

Worcester Bosch Which? Best Buy

As one of the most credible and respected consumer awards - it's an award, unlike others, which you simply can't buy.

The brand won the “best buy” award based on feedback from actual real humans (not pretend ones). They also gathered feedback from over 100 installers. Moreover, the brand's boilers received several high 5-star ratings the consumer choice organisation considers most important to consumers, including full marks for their build quality and availability of parts and spares.

If your Worcester Bosch boiler's losing pressure, get a fixed price replacement, online.

How much will the installation of the best combi boilers cost? Check out our new boiler costs guide for the full rundown. 

#2 Viessmann Combi Boilers (2nd Best boilers)

Viessmann is already an astronomical force in the European boiler market and also lead the way in commercial boiler installations. Now they’re here to bestow their majestic German engineering upon the UK domestic market providing your home with a new boiler so good, you can forget about it for good this time.

Viessmann’s 2021 combi boiler range & overviews:

Viessmann Model Kilowatt (kW) outputs
Vitodens 050-W - 29kW 35kW
Vitodens 100-W 26kW 30kW 35kW
Vitodens 200-W - - 35kW
Vitodens 111-W 26kW - 35kW

Boiler not working? Fancy a Viessmann? Get your fixed price from £1,695, online. We can fit within as little as 24 hours.

Fixed Price Boiler Quote

Viessmann Vitodens 050-W Gas Combi Boiler

Available in two kW outputs suitable for any home requiring a new combi boiler, the Viessmann Vitodens 050-W is the trusty workhorse of the Viessmann family. It has a price to compete with boilers that don’t scratch the surface of its quality whilst maintaining high component standards – most importantly of all, a stainless steel heat exchanger (essentially a part in other boilers that’s likely to break and Superman would struggle to crack this one). Oh – and it has a Which? Best Buy award.

Like the Viessmann Vitodens 050-W? Get a fixed online price, including installation from £1,695.

Viessmann Vitodens 100-W Combi Gas Boiler

Everything that makes its little brother Vitodens 050-W the super boiler it is and more. The Viessmann Vitodens 100-W should be any homeowners go-to combi boiler. A familiar endorsement from ‘Which?’ for its remarkably high end internal parts, a class A rating for efficiency, back-lit LCD display, low fan speed for quiet operation and low CO2 emissions to help ease your carbon footprint and conscience. This is Viessmann’s Lebron James.

Like the Viessmann Vitodens 100-W? Use our boiler quote calculator (no personal details needed).

Viessmann Vitodens 200-W Combi Boiler

Meeting every demand a boiler buyer could possibly have of their combi boiler. The Vitodens 200-W is perfectly suited for the larger detached and semi-detached homes. It holds every feature and perk of Viessmann boilers before it whilst also boasting a colour touch screen display, smart thermostat compatibility and up to an incredible 98% efficiency rate.

Like the Viessmann Vitodens 200-W? Get a fixed online price

Viessmann Vitodens 111-W Combi Boiler

The only thing Viessmann can be accused of is a lack of imagination when it comes to naming their boilers, but their quality does all of the talking. The Vitodens 111-W is a monstrous storage combi – essentially rendering it a kind of beautiful Frankenstein boiler – half way between combi and regular boiler delivering a ludicrous 18litres of hot water per minute. Lucky enough to have that huge house you always wanted? Get luckier and get yourself the Vitodens 111-W.

Like the massive Viessmann Vitodens 111-W? Get a fixed online price

Typical Viessmann Combi boiler prices 2021 (ours are the best!):

Viessmann Model Our Price   
Vitodens 050-W 29kW £1,795
Vitodens 050-W 35kW £2,175
Vitodens 100-W 26kW £2,247
Vitodens 100-W 30kW £2,404

Vitodens 100-W 35kW £2,639
Vitodens 200-W 35kW £2,750
Vitodens 111-W 26kW £3,180
Vitodens 111-W 35kW £3,421

Please note: The above prices assume a straight forward swap of a new, replacement combi boiler. To get the best accurate price, click the get quotes button. Or, for a massive, in-depth article on prices, check out our new boiler costs article.

If time eluded you and you didn’t have time to read the life changing Viessmann overview above, then do read this brief conclusion.

Want to save money and energy on your heating bills? If so, you should consider installing one of the best smart thermostats.  

If Viessmann's really are the best gas combi boiler, why are they so cheap?

Heatable has a unique business model, allowing us to offer all our Viessmann’s with a 10-year warranty at mind bogglingly low prices.

But truthfully – Viessmann boiler prices will very shortly be on the rise and such bargains much harder to come by. Right now, Viessmann is priced so well to increase their exposure to Britain’s domestic boiler buyers but as their quality becomes more than just rumour – their prices will inevitably rise to reflect just how premium of a product they really are. The best combi boiler of 2020, may soon become the most expensive.

Viessmann boilers sponsor Huddersfield Football Club and since this engagement, the Huddersfield players have been so distracted by the beautiful heating machines in their homes, they’re practically guaranteed relegation from the Premier League this year – all without a care in the world. That’s the power of Viessmann.

*2021 update - Huddersfield were indeed, relegated. 

Viessmann boilers quality comes from within – literally. A boiler is the sum of all its parts and internal components make or break them.

Viessmann never compromises on the quality of their build - it’s a German thing. They only accept the best. Their boiler range is littered with endorsements from Which? all so readily backing up their already unrivalled features and statistics.

Did you know our boiler installation cost calculator only takes 60 seconds to complete? Using a series of multiple-choice questions, it can provide you with a fixed price on a range of budget-friendly boilers. 

Did we mention that Viessmann is the UK’s most reliable boiler? If nothing else swings it for you, that alone, should.

What's more, Viessmann offers some of the best boilers in class when it comes to efficiency too.

The Energy Saving Trust said:

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 emissions a year.

Convinced that the Viessmann combi range is the best for you? Get fixed online price today and get your installation as quickly as tomorrow.

Read our Worcester Bosch vs Viessmann Boilers review if you need some help in choosing between these two popular brands. 

Have you got limited space in your home? Check out our guide on the best small boilers


Want an exact price on a new boiler? Use our boiler quote calculator (your fixed price will appear on screen).

#3 Vaillant Combi Boilers (3rd Best combi boilers)

Another proud owner of a Which? Best Buy award and huge player in the British boiler market. Vaillant is a time served and well respected boiler manufacturer and certainly amongst the premium contenders.

Vaillant combi boilers are made in the UK to impeccably high standards, they’re already in a staggering amount of UK homes, offer excellent warranties, and are loved by boiler installers too.

Vaillants 2021 combi boiler range & overviews:

Vaillant Model Kilowatt (kW) outputs
ecoTEC exclusive - - 35kW 43kW
ecoTEC plus 25kW 32kW 35kW 38kW
ecoTEC plus store - - -

ecoTEC pro 24kW 28kW 30kW -
ecoFIT pure - 25kW 30kW 35kW

Vaillant ecoTEC exclusive Combi Boiler

Available in outputs at the higher end of the scale; 35kW and 43kW, the ecoTEC exclusive is a premium combi boiler for larger homes which boasts an impressive 17 litres of hot water per minute. Certainly impressive if you like lotsa' hot water.

Vaillant ecoTEC plus Combi Boiler

A broad range of kW outputs starting from 25kW makes Vaillant’s ecoTEC plus the combi allrounder for almost any small to medium homes. Excellent efficiency ratings, premium components and the addition of the Quiet Mark award for quiet operation make this Vaillant’s flagship boiler.

Vaillant ecoTEC plus store Combi Boiler

A beast of a storage combi boiler that’s premium in every manor. A hot water delivery rate of up to 20 litres per minute that you would struggle to find elsewhere makes this an outstanding choice for larger homes if you don’t want to, or have the room to fit an additional water storage tank.

Curious to know which condensing boiler brand performed worst? Find out in our report of the worst boilers

Vaillant ecoTEC pro Combi Boiler

The perfect combi boiler solution for small to medium homes with the kW model’s coming in three different outputs to suit all. A bright LCD display makes the ecoTEC pro super simple to use and it also comes with a Quiet Mark award so it’s not going to wake you up whilst warming your home in the morning.

Vaillant ecoFIT pure Combi Boiler

Another super-efficient combi boiler suitable for almost any sized home with the added bonus of being extra compact if you’re shy on cupboard space or a boy wizard lives under your stairs. It’s clever too – automatically reducing its energy usage to lower your bills.  

Premium Vaillant boiler, premium Vaillant price? Afraid so.

If you’re splashing out on a Vaillant then there is a very slim chance that your new boiler will disappoint but splashing out you will be.

Unfortunately, Vaillant’s price range does often make you feel like you've stood up too quickly so may well hold the more savvy shopper at bay.

They sit firmly behind Worcester and Viessmann in the boiler pecking order but are so often priced above and beyond them.

Recommended: Check out our top 10 list of the best boiler manufacturers for a complete rundown on the best combi boiler makers. 

It’s difficult to put our finger on why they’re priced so highly – perhaps five different combi boilers has spoilt their broth but whilst Vaillant have to make our best boiler list due to their undeniable quality, their pricing structure does make you wonder if boiling your kettle and washing in the sink is really that bad?

Do you have a Vaillant and are experiencing the F28 code? Read our full guide on the Vaillant F28 error

#4 Ideal Combi Boilers (4th Best boiler brand)

Joyful wordplay aside, an Ideal combi boiler might just be the ideal boiler for your home.

Ideal boilers have been a mainstay in the British boiler market for what seems like an eternity. Picture a horse that relentlessly finishes in the top 6 at the Grand National but never quite gets its nose in front – no cigar but you know that horse is from a damn good stable.

Ideal is all about inclusivity and range – their combi boilers range from budget to bedazzling and everything in between meaning they cater to the folks funding their boiler replacement with change found down the side of their couches, as well as those looking for the best boiler money can buy (see; Ideal Vogue).

Ideal’s 2021 combi boiler range & overviews:

Ideal Model Kilowatt (kW) outputs
Logic 24kW 30kW 35kW
Vogue Gen2 26kW 32kW 40kW
Vogue Max 26kW 32kW 40kW

Do you have a back boiler and want it replaced with a modern combi boiler? Ideal looking like an ideal choice? Get a fixed online price

Ideal Logic Combi Boiler

Ideal, Logic, Vogue. Ideal’s marketing team don’t like unnecessary syllables and love assigning words to their products that already hold positive connotations.

Fortunately, their technical team do tend to back this up.

The Logic combi is without a doubt a logical choice for any grudge purchase boiler installation. The odds of your boiler breakdown being expected and affordable? We’ve checked, it’s 3%. The Ideal Logic is a no thrills, solid boiler that’s popular for its price to quality ratio. Ideal offers a 2-year standard warranty providing you with required peace of mind – not bad for a dual award winner.

Ideal Logic combi's best boiler perks:

  • Made in the UK... so you know it's good
  • Compact in size (ideal for cupboards)
  • Roughly as difficult to program as peeling a banana
  • Won the Queens Award in 2013
  • Won Good Housekeeping Award 2013 & 2017
  • 2 year warranty as standard 

Want the best price on a new Combi Boiler? Get a fixed online price with installation within 24 hours.

Ideal Vogue Combi Boiler

Weary of churning out their regular award winning boilers, Ideal set out to make a boiler to break the mould.

The Ideal Vogue Gen2 is Ideal’s best, premium offering, also picking up numerous awards, it has been blessed with internal component upgrades, a back lit LCD colour display, a standard 10-year warranty, built in frost protection and an endorsement from the Energy Saving Trust for its outstanding efficiency and global warming protest organisational skills.

Ideal Vogue Max Combi Boiler

If it isn’t broken, don’t fix it. Ideal know that it’s just plain logic. So their Vogue Max is just their regular Vogue but with an added Ideal approved water filter, magically increasing their already whopping 10-year warranty to an unprecedented and industry leading, 12-years. It's the best combi boiler in its class in terms of warranty length vs cost.

A note on the head turning, heart-breaking, bone chilling aesthetics of the Ideal Vogue:

This Adonis of a heating machine looks like a groomed wild boar, purring with unshakeable self-certainty but at the same time, exuding the divine grace of a gliding swan. Some of the UK’s oldest ducks cower in shame at the ease of which water rolls off this machines back.

Typical Ideal Combi Boiler prices (we offer the best online prices, period!):

Ideal Model Price (Guide)  
Logic Combi 24kW £1,650
Logic Combi 30kW £1,845
Logic Combi 35kW £2,245
Vogue Gen2 26kW £2,350

Vogue Gen2 32kW £2,550
Vogue Max 26kW £2,550
Vogue Max 32kW £2,690
Vogue Max 40kW £2,960

Please note: The above prices assume a straight forward swap of a new, replacement combi boiler. To get the best accurate price, click the get quotes button.

For the best budget combi boiler, as of 2020, we would recommend the Alpha E Tec, but for those looking for something a little more premium, then the Viessmann or Worsceter range is certainly worth looking into. These are some of the best boiler brands available, and that's why we fit them. You won’t find a better combi boiler in the Alpha boilers range in 2021.


Want an exact price on a new boiler? Use our boiler quote calculator (no personal details needed).

#5 BAXI Combi Boilers (5th Best combi boiler)

Nobody has ever been struck with such elation after being offered a BAXI boiler that they’ve moonwalked to work the next day and offered their colleagues a poorly baked lemon drizzle cake – but perhaps they should.

Baxi might not be considered amongst the premium boilers of the market but they certainly have some premium products backed up by award winning customer service and excellent warranties so if you’re looking for a bargain, you might just find it in a BAXI.

BAXI combi boiler range & overviews:

BAXI Model Kilowatt (kW) outputs
100 Combi 24kW 28kW - -
200 Combi  24kW 28kW - -
400 Combi 24kW 28kW -

600 Combi 24kW - 30kW 36kW
Duo-tec 24kW 28kW 33kW 40kW

EcoBlue Advance 24kW 28kW 33kW 40kW
EcoBlue + 24kW 28kW 33kW -
Platinum 24kW 28kW 33kW 40kW


We know what you’re thinking.

So many Baxi boilers and so little time and why do Baxi avoid prime numbers in the combi models like they know something we don’t?

Baxi has more combi boilers that we would care to run through but if you’re looking for top quality and aiming for that reassuring 10-year warranty mark, make sure you aim for the Baxi 600, the Baxi duo-tec, the Baxi EcoBlue range or the Baxi Platinum.

Consider avoiding the Baxi 100, 200 & 400 range if you’re looking for a premium standard and long warranty.

If your radiator is cold at bottom, it may be a sign of a faulty boiler valve, in which case getting your new boiler replaced may be appropriate, check out the Worcester Bosch Greenstar 30i, which you can purchase through us. 

Interested in a Baxi? Read our Baxi Duo Tec 28 combi boiler review and the Baxi 600 Combi boiler review

The Best Boilers - Our Conclusion 

This guide's purpose is to help you make an informed decision about your new boiler purchase. Let's face it, you aren't going to be buying a new one that often, so you want to ensure it lasts the test of time. 

That's why the boiler's we have presented have been thoroughly vetted based on the factors that truly matter: reliability, customer reviews, availability of parts, price range, and efficiency ratings. 

If you think your boiler is at the end of its life, then it usually makes financial sense to get it replaced sooner rather than later, since repair costs can quickly start to mount. Not only that but modern A-grade boilers offer superior efficiency, helping you save more money on your heating bills.

The best gas boilers offered by leading manufacturers such as Worcester Bosch and Viessman will also come with a brand new warranty (or guarantee in the case of Worcester), so you can have the peace of mind that if something does go wrong, you'll be covered - sometimes for as long as 10 years. 

Best Combi Boilers (By Model)

  • #1 Worcester Bosch Greenstar CDi Compact 
  • #2 Viessmann Vitodens 050-W Combi 
  • #3 Ideal Logic+ Combi 
  • #4 Baxi 600 Combi 
  • #5 Alpha E Tec 

The above is our definitive list of the best combi boilers available from each of the manufacturers in our best boiler brands ranking. 

In our view, these are the best boiler models offered by some of the UK's biggest and most reputable boiler manufacturers. They offer the perfect combination of excellent customer reviews, warranty periods, technical brilliance, efficiency, and power.

Having issues with your combi boiler? Read our boiler problems and solutions for quick troubleshooting guidance. 

What is a combi boiler & how does it work? 

Coldwater 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.

Your home’s thermostat is able to detect the temperature in your home and when it detects your properties temperature has dropped, it is able to send a signal to the boiler. In response, the boiler will fire up, heat the water and pump it through the system to the radiators.

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 within the home, or another hot water outlet such as the shower, a component within the boiler called the diverter valve will divert hot water to the taps 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.

Want to learn about the future of heating in the UK? Check out the latest innovation of hydrogen boilers.  

Frequently Asked Questions 


Best central heating boiler

The best central heating boilers on offer in 2020 are: 

  • #1 Worcester Bosch Greenstar CDi Compact
  • #2 Viessmann Vitodens 050-W Combi 
  • #3 Alpha E Tec

These boilers are particularly good since they are available as both system boilers and combi boilers. 

The above boiler manufacturers have been recommended based on their quality, reputation, and customer reviews. 

For instance, Worcester Bosch has been a Which? Best Buy award winner for 10 consecutive years, offers a 10-year guarantee and has been a reputable brand in the UK for generations. 

Viessmann is another high-quality boiler brand, offering impeccable German engineering, while Alpha is an excellent value boiler brand, that offers technical superiority for its price point. 

Read our complete guide on central heating boilers to learn more. 

Which is the best combi boiler for my home?

Batman would be pushing it if he wanted a combi boiler for Wayne Manor.

Fortunately, though, modern combi boilers will be perfect for almost any home – from 1 bedroom flats to 6 bed detached houses.

Please note: The exact boiler suitable for your home depends on a variety of factors unique to your situation. 

But, if you've got a whopping great mansion with multiple bathrooms and shower units, we'd suggest you look for an alternative. For homes of that size, you'd be better looking at quotes for a new regular or system boiler.

They store hot water in large tanks (separate from the boiler) and feed the water outlets at an even rate. If you had a combi boiler, and you tried to run 3+ baths at the same time, it'd likely trickle out rather than blast.

Here’s a quick glance at which combi boiler is best for your home in 2020:

Best combi boiler for a small flat/apartment

Best Boiler: Worcester Bosch Greenstar 25i
Best Boiler Size: 25kW

25 Kilowatts of pure Ideal will perform well for smaller properties, providing heat and hot water on demand. It’s also backed up by outstanding customer reviews and through Heatable, packs a whopping 5 year warranty.

Best combi boiler for a 2 bedroom house

Best Boiler: Worcester Bosch Green Star CDi Compact 
Best Boiler Size: 28kW

A 28kW CDi Compact with a 10-year warranty effortlessly glides into a 2 bedroom home. It’s the manufacturer's bestseller, isn’t at all bad to look at, and remarkably simple to operate.

Best combi boiler for a 3 bedroom house

Best Boiler: Viessmann Vitodens 050-W
Best Boiler Size: 29kW

German design at its best. The Vitodens 050-W 29kW is perfect for three-bedroom homes and not only more powerful than it’s competitors but officially more reliable too. 

Read the Vitodens 050-W Combi Boiler Review.

If you live in an average-sized home, see our guide on choosing the best boiler for a 3 bedroom house

Best combi boiler for a 4 bedroom house

Best Boiler: Viessmann Vitodens 050-W
Best Boiler Size: 35kW

Eternal reliability, award-winning and a 10-year parts and labour warranty – that’s basically like Helen Mirren personally looking after your homes heating requirements and keeping a close eye on your energy bills.

Best combi boiler for a 5+ bedroom house:

Best Boiler: Viessmann Vitodens 100-W
Best Boiler Size: 35kW

The only other building in the world that harbours more of these boilers than Viessmann’s actual factory is Buckingham Palace, Her Majesty has at least 1 per every member of staff and three for every dog. In all seriousness though, it is genuinely the boiler of choice for the palace and rightly so. It’s a peerless and powerful boiler built entirely from premium components.

Read the Vitodens 100-W Combi Boiler Review.

Want to have your combi boiler moved to a different location? Check out "cost of moving boiler" guide.


Which is the best combi boiler by size?

If you’re in the 99% of readers who have power-scrolled through this article picking up keywords like Good, Combi and Batman…

Then this quick overview of best combi by size is the one for you.

Best small combi boilers:
#1: Viessmann Vitodens 100-W 26kW
#2: Baxi 600 – 24kW / 30kW

Best large combi boilers:
#1: Viessmann Vitodens 100-W 35kW
#2: Worcester CDi Classic 38kW

Best offensively large, powerful combi boilers:
#1: Worcester CDi Highflow 44kW / 55kW
 Viessmann 111-W 35kW

Want to know kW you need for your home? Check out our "what size boiler do I need" guide.


Who, What, Why, Where, When, Which?

Who is Which? anyway?

Which? are an independent consumer advise platform that offers UK homeowners and consumers impartial advice on an array of products and services. They are undeniably well informed and absolutely love question marks.

Some special products, of high birth and royal blood, even manage to secure themselves a prestigious nod from the mighty Which – the Which? Best Buy Award, with Worcester Bosch having held that title for 10 consecutive years. 

You can check the latest deals on Worcester Bosch boilers here

They use their annual boiler survey to award the best boiler, which is based on feedback from thousands of UK installers and homeowners. 

Getting yourself a bargain boiler is one thing. But getting yourself a well-priced Which? Best Buy boiler is like dropping the bandit.

Use this clickable form to get a fixed price on the screen instantly. 

Advantages of combi boilers

If you don’t already have a combi boiler, then you might feel left out and be wondering what all the fuss is about.

But we can reliably inform you that a combi boiler does indeed, live up to the hype.

They provide instant hot water for both your central heating and hot water demands. You might call them a com-bi. It loves both.

But it’s not just having the ease of instant hot water without having to give a giant metal tank one hours’ notice before you want a bath as though Robocop was your butler.

A combi boiler is also remarkably efficient at heating the water – up to 98% efficient. We had a mathematician check this number and it’s just 2% less than 100%! That makes it superior to immersion heaters

The efficiency offered by a combi isn’t just a lovely number though, it can make you some outrageous savings on your energy bills – savings you’ll actually notice in monetary value, not like the saving between Asda and Tesco on petrol.

They’re also much kinder on the environment so the birds outside your house choking on Monster Munch packaging have one less thing to worry about.

Still not sure which boiler is right for you? Check our guide all about the main types of boilers

Cost of combi boiler installation

The cost of a new central heating boiler is dependent on a variety of different factors, these include the following:

  • The type of boiler you have installed e.g. combi, regular or system.
  • The boiler model you choose e.g. mid or premium range.
  • If want to relocate your boiler e.g. from the garage to the attic.
  • If you want to convert your boiler e.g. from combi to regular.
  • Any add-ons you purchase e.g. filters, smart controls etc.

Check the latest prices on our combi boilers here

One of the most common and straightforward types of central heating boiler installations is a straightforward combi swap i.e. replacing your old combi with a new combi. This is much simpler than replacing a combi with a system boiler.

This is due to conversions being more complex to install, taking more time, requiring more labour and more materials. More everything.

The boiler model you choose also has an impact on the cost and at Heatable we offer more value-orientated brands such as Alpha, as well as award-winning, premium brands such as Worcester Bosch and Viessmann.


How to get the best combi boiler deal in 2021

Without boasting, get your new boiler quote and buy from us.

We're an online, nationwide boiler installation business with 500+ 5 star reviews from a shed load of happy customers.

Because we're online, our overheads are low which means we pass those savings on to our customers, ensuring they're always getting the best deal on a new combi boiler. 

More advice

New boiler deals

Buy your new boiler, better

Get a fixed price on a Which? Best Buy in minutes

Heatable is registered in England and Wales No. 08804726 (VAT No. GB205805920 ). Trading address is 1 Station Road, Great Sankey, Warrington, Cheshire, WA5 1RH. Heatable acts as a credit broker (not as a lender) and offers credit products through a panel of lenders. Heatable is authorised and regulated by the Financial Conduct Authority (reference no. 805259).

[1] Price based on a like for like combi swap in a 2 bed, 1 bathroom terraced home with a standard flue

[*] Installation dates are subject to installer availability

[ยน] only available on combi boiler installations

Financial Support: If you are in receipt of certain benefits, you may be entitled to claim a free boiler grant.