Here we review the UK’s most reliable combi boilers and explain why each one made the cut. From efficiency to durability, we highlight what sets these top boilers apart, helping you find the perfect fit for your home heating needs.
Looking for a boiler that won’t give up on you when the cold weather hits? Well, you’ve come to the right place! We’ve rounded up the top combi boilers available in the UK, so you can rest easy knowing your home will stay warm, no matter how frosty it gets outside.
Whether you’re after efficiency to save on bills, reliability to avoid mid-winter breakdowns, or a compact design to fit in those smaller spaces, we’ve got you covered.
And the best part? These boilers won’t have you installing a bulky water cylinder! Ready to find your perfect match? Let’s dive in!
Key points:
Worcester Bosch, Veissmann, Ideal, and Baxi are some of the most reliable combi boiler manufacturers.
Modern combi boilers are much more efficient than older models.
You’ll save more money the more efficient your boiler is.
Combi boilers save you from having to install a separate water cylinder.
Looking for a combi boiler that doesn’t break at the first sign of winter? Look no further than our list of reliable combi boilers, which you can use to find a boiler you can rely on.
If you want to reduce your energy bills and emissions too, it just so happens that the most reliable combi boilers are very efficient, making them ideal for exactly this. Before we get started, let’s first break down how we’ve picked the most reliable combi boilers on the market.
How do we define what the most reliable boiler is?
We’ve looked at everything there is to look at when it comes to picking combi boilers you could bet your house on.
So that’s the brand, expected longevity, how efficient a boiler is, warranty length, and feedback from homeowners and the heating engineers that install the boilers themselves.
We didn’t leave a single stone unturned.
Also, we’ve included information on how boilers perform according to different house sizes, because you don’t want an underpowered boiler leaving you shivering in your shower when it can’t provide enough hot water.
What is a combi boiler?
First introduced to the UK in the 1960s, combi boilers revolutionised the way we heat our homes by doing away with the need for a bulky water tank.
They heat up water on demand, meaning the minute you turn on your shower, a combi boiler kicks in to provide warm water almost instantaneously.
And because you don’t need a tank, a combi boiler takes up much less space. The downside to a combi boiler is that unless it’s an especially powerful model, it might struggle to provide hot water for multiple bathrooms all trying to shower at the same time.
Are combi boilers good for the environment?
How good a combi boiler is for the environment depends on whether it’s electric or powered by gas, as the latter is a finite fossil fuel that releases carbon emission when burned.
But these days, basically all modern combi boilers are much more efficient than their older ancestors, and are a lot better at minimising emissions. Especially combi boilers that use condensing technology, which means the boiler captures and reuses heat that’d otherwise be wasted.
If you have a combi boiler that uses liquefied petroleum gas (LPG), then your combi boiler will be even better for the environment, because LPG is a cleaner fuel than natural gas.
What are the most reliable combi boilers?
Here are our picks of the most reliable combi boilers you can get right now, before we break down each choice in more detail:
Most reliable warranty: Viessmann Vitodens 100-W
Most reliable boiler for a large house: Worcester Bosch Greenstar 8000
Most reliable boiler for a small house: Viessmann Vitodens 050-W
Best value for money: Baxi Platinum Combi
Best reviewed combi boiler: Ideal Vogue Max C40
Most reliable combi boilers by model
These are the most reliable combi boilers on the market. Each one stands out for different reasons, but all are models you can rest assured will keep your home warm and toasty for years to come.
#1 Viessmann Vitodens 100-W
Our verdict: The most reliable warranty on the market
Warranty: Up to 12 years | Energy Efficiency Rating: A | Output Rating (kW): Available in 26, 30, and 35 kW options | Water Flow Rate (litres/minute): Up to 14.1 depending on the model | Size H/W/D (mm): Approximately 700 × 400 × 350 | Price: Starts from around £1,250 (may vary based on output and supplier).
Pros:
Amazing warranty period – 12 years!
Very efficient, with a rating up to 98%.
ErP A-rated for both heating and hot water efficiency.
Easily controlled via your phone
Cons:
Higher cost than more affordable models
Fewer output ratings than some of the other models on this list
We’ve featured the Viessmann Vitodens 100-W in more than one ‘best of’ list, and that’s for good reason — it’s an excellent boiler with exceptional reliability.
So reliable in fact, that Viessmann saw fit to give it a whopping 12-year warranty, when the boiler is installed by a Viessman-trained engineer (psst, we’ve got plenty here at Heatable).
It’s clear Viessmann trusts the Vitodens 100-W to last, and we do too, such is the quality of the components used in it. A stainless steel heat exchanger, for example, all but guarantees longevity. Having one in a boiler reduces the risk of corrosion and the build up of limescale.
And this boiler comes with a built-in shock arrestor too, protecting the pipes in your home from damage if the water flow suddenly stops.
What’s great about the Vitodens 100-W too is that it’s more than happy sitting inside most standard kitchen cupboards. Sure, we love boilers here at Heatable, but we fully understand that most people won’t want a boiler sticking out!
Who might the Vitodens 100-W not be for?
For all this reliability, warranty, and world-class components, you do pay a premium — buying and installing the smallest Vitodens 100-W, the 26 kilowatt (kW) model, will cost you £2,250 (including installation).
So if you’re on a tighter boiler budget, the Vitodens 100-W might not be for you.
Also, its array of advanced features means this boiler might actually be overkill for smaller homes or those with simpler heating needs.
#2 Worcester Bosch Greenstar 8000
Our verdict: The most reliable boiler for a large house
Warranty: Up to 10 years | Energy Efficiency Rating: A | Output Rating (kW): Available in 30, 35, 40 and 45 kW options | Water Flow Rate (litres/minute): Up to 17.9 depending on the model | Size H/W/D (mm): Approximately 780 × 440 × 365 | Price: Starts from around £2,500 (may vary based on output and supplier).
Pros:
One of largest combi boilers you can get
Can provide hot water to multiple bathrooms at once
Up to 94% efficiency rating
Looks fantastic
Extremely high water flow rate
Cons:
Biggest upfront cost of any boiler on this list
Potentially too big to fit inside a cupboard
The Worcester Bosch Greenstar 8000 is the ultimate combi boiler for high heating needs and larger homes. It’s capable of some pretty astonishing heating feats, especially when you go up to the maximum power rating of 45 kW.
Once you get here, a Greenstar 8000 will comfortably heat a house with 15 or more radiators, a feat normally reserved for system boilers (a boiler that requires a separate water cylinder).
It’s also a boiler you can rely on to almost never lose pressure when you need it, thanks to the crystal-clear digital interface that tells you when you need to top up pressure. Many other boilers, on the other hand, simply tell you after the fact — not ideal when you’re in the middle of a shower in winter and the hot water cuts out.
And, like the other boilers on this list, you’ll get a fantastic warranty with the Greenstar 8000 — 10 years as standard. A lot can happen in a decade (has it really been that long since Brazil lost 1-7 to Germany?), but with this boiler, you know you won’t need to shell out during.
If you’re into your smart features, there’s also plenty to love about the Greenstar 8000’s technology. It has full compatibility with the Bosch EasyControl smart thermostat, which links to an easy-to-use app (downloadable from the App Store and Google Play).
In layman’s terms, you can use your phone to kick-start the boiler wherever you are — perfect for when you’re heading back home after a holiday or from work.
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 might the Greenstar 8000 not be for?
This boiler is big, and though it can be wall-hung, will probably struggle to fit inside your average kitchen cupboard (it does look very good though, so you might not want to hide it).
It’s not cheap either, but that’s to be expected from a boiler this size from a premium manufacturer.
If you’ve got a small or medium-sized home too, the Greenstar 8000 is likely too powerful, meaning spending the extra on it might not actually be worth it.
#3 Viessmann Vitodens 050-W
Our verdict: The most reliable boiler for small homes
Warranty: Up to 10 years | Energy Efficiency Rating: A | Output Rating (kW): Available in 19, 25, and 35 kW options | Water Flow Rate (litres/minute): Up to 12.2 depending on the model | Size H/W/D (mm): Approximately 704 × 400 × 350 | Price: Starts from around £900 (may vary based on output and supplier).
Pros:
One of the most efficient boilers with a 97% rating
Up to 10-year warranty
Can be operated from your phone
Integrates seamlessly with smart thermostats
Cons:
Not enough power for medium and above size homes
Won’t work well in areas with low water pressure
Need a new boiler for a smaller home? Look no further than the brilliant Viessmann Vitodens 050-W, a highly regarded member of the Vitodens family.
It’s an absolute gem of a boiler for smaller homes with simpler heating needs, and will meet your hot water needs with ease.
Oh, and the Vitodens 050-W is very reliable to boot, using many of the same high-quality components found in the more expensive 100-W and 200-W models in the range.
That’s a patented Inox-Radial stainless steel heat exchanger by default then, so you can rest assured that the curse of corrosion and limescale build-up will be kept at bay for a long, long time.
Viessmann won the Which? Best Buy Award from 2017 to 2020 as well, which is one of the most prestigious awards a boiler can win. Trustpilot proves that love is in the air for Viessman too, with an average score of 4.4 out of 5 from nearly 5,000 reviewers (a genuinely impressive result for a company that’s still a relative newcomer in the UK).
Efficiency is always a key part of what makes Viessmann boilers so good, and the story is much the same here with the Vitodens 050-W. It’s A-rated for efficiency and hits 97% — this means for every £1 you spend on heating, the Vitodens 050-W converts the fuel into 97p’s worth of heating.
Old boilers can have efficiency ratings as low as 60%. Imagine spending £1,000 on heating your home and realising you’re effectively chucking £400 out the window. That’s why you want an efficient boiler so you can save more money on your energy bills.
Who might the Vitodens 050-W not be for?
Larger homes might struggle to keep warm with a Vitodens 050-W alone, because it’s not quite powerful enough to provide the right level of heating.
It’s also still a premium boiler, even though it’s cheaper than the slightly larger Vitodens 100-W. You pay for the near-guaranteed reliability, but as you’ll see below, you don’t always need to spend extra to get a reliable boiler.
#4 Baxi Platinum Combi Boiler
Our verdict: The best value for money boiler
Warranty: Up to 10 years | Energy Efficiency Rating: A | Output Rating (kW): Available in 24, 33, and 40 kW options | Water Flow Rate (litres/minute): Up to 16.4 depending on the model | Size H/W/D (mm): Approximately 780 × 450 × 345 | Price: Starts from around £930 (may vary based on output and supplier).
Pros:
Amazing value boiler
A-rated for efficiency at 92%
10-warranty for parts and labour
Cons:
Quite large; might be difficult to fit inside a cupboard discreetly
Won’t work as effectively in large homes with multiple bathrooms
The Baxi Platinum Combi Boiler range has the best value out of any manufacturer on this list, costing £200–£350 less than equivalent models in the Worcester Bosch, Viessman, or Ideal ranges.
Don’t for a moment think that a lower price means a sacrifice in reliability — far from it in fact. Baxi, a legendary name in British boiler folklore, has supreme confidence in the reliability of its Platinum combi boilers, offering customers a 10-year warranty as standard.
The parts used are top notch too. With high-quality brass hydraulics and a stainless steel heat exchanger, Baxi’s commitment to components that last is clear to see.
You won’t find an advanced LCD screen giving you a wealth of information, but every boiler in the Platinum Combi range can be controlled by your phone. Also, Baxi introduced its EasyFil component into the range, which makes it super simple to top up boiler pressure yourself if it dips too low (no need to call an engineer).
Who might the Platinum Combi Boiler not be for?
Those who want a boiler suitable for a large house might want one with extra features, such as more intuitive controls and better integration with smart technologies. In this case, it might well be worth spending the extra on a boiler like the Worcester Bosch Greenstar 8000.
Also though the difference is just two percent, the Greenstar 8000 is a little more efficient at 94%. Over a certain period of time, the Greenstar 8000 could actually save you some more money, albeit a pretty small amount more.
Join Thousands of Satisfied Customers:
We’re proud to be Which? Trusted Traders with over 10,000 glowing reviews on Trustpilot. Check out our Reviews and Testimonials page and watch Adrian’s video testimonial below to see why so many trust us for their heating needs.
#5 Ideal Vogue Max C40
Our verdict: The best reviewed combi boiler
Warranty: Up to 12 years | Energy Efficiency Rating: A | Output Rating (kW): Available in 34, and 40 kW options | Water Flow Rate (litres/minute): Up to 16.4 depending on the model | Size H/W/D (mm): Approximately 740 × 445 × 330 | Price: Starts from around £1,570 (may vary based on output and supplier).
Pros:
A-rated efficiency with a 93% rating
Built-in frost protection
10-year default warranty, up to 12 years if installed by a Max-accredited installer
Great price point for what you get
Cons:
Likely overkill for smaller homes
Smart controls cost extra
You need to use a Max-accredited installer to get the 12-year warranty
Ideal is a well-established British boiler brand that over the last century or so, has mastered the craft of keeping your home warm. There’s a reason the company placed highly in our list of the best boiler brands, but that’s not what got Ideal a spot on our list of the most reliable combi boilers.
No, what got Ideal here was its absolutely stellar reputation among the British public. Out of every manufacturer on this list, Idea has far and away the best reviews on Trustpilot.
How good? Mind-bogglingly good — as of October 2024, Ideal has a 4.8 out of 5 rating, based on reviews from nearly 49,000 people. 95% of customers gave Ideal 4 or more stars, in other words.
As for awards, well Ideal keeps on winning them it seems — in 2017, Ideal received the Good Housekeeping Award, and it won the Queens Award in 2013 and 2019.
We can see why, especially when you look at boilers like its Ideal Vogue Max C40. This highly reliable boiler can provide up to 16.4 litres of hot water a minute, which is ideal (we made it pretty far without using that adjective) for larger homes.
It works great with smart thermostats such as Nest too, which helps you save energy and even more money on your heating bills.
The C40 (and other models in the Vogue Max range) has a simple full-colour LCD display screen that gives you all the information you’ll need — a pressure gauge and a service time that reminds you to book your annual service so you can keep your warranty valid.
Who might the Ideal Vogue Max C40 not be for?
Although the Ideal Vogue Max C40 can be wall mounted, its bulkier-than-usual size (compared to some other combi boilers) means it might not fit easily in a kitchen cupboard. This isn’t ideal for people who want a discrete boiler installation.
It’s also probably too much for smaller homes because the high heating output is likely overkill.
Most Reliable Combi Boilers Comparison Table:
Boiler Model: | Viessmann Vitodens 100-W | Worcester Bosch Greenstar 8000 | Viessmann Vitodens 050-W | Baxi Platinum Combi Boiler | Ideal Vogue Max C40 |
Best For: | Warranty | Most reliable for larger homes | Most reliable for smaller homes | Best Value | Best reviewed boiler |
Efficiency | 92% | 94% | 97% | 92% | 93% |
Power output (kW) | 35 | 30-45 | 25 | 24-40 | 34-40 |
Warranty | 12 | 10 | 10 | 10 | 12 |
Water flow rate (litres/min) | 14.3L flow rate | Up to 17.9L flow rate | Up to 12.2L flow rate | Up to 16.4L flow rate | Up to 16.4L flow rate |
Size | 700mm (h) x 360mm (d) x 400mm (w) | 780mm (h) x 365mm (d) x 440mm (w) | 700 (h) x 300 (d) x 400 (w) | 740 (h) x 345 (d) x 450 (w) | 740 (h) x 330 (d) x 445 (w) |
Weight | 35kg | 41kg | 35kg | 29.2kg | 43.4kg |
Next Steps For Your New Boiler Journey:
When planning to install a new boiler for your home, there are several important factors to consider. Make sure to refer to the following guides to help you make informed decisions:
To dive deeper into these topics, head over to our advice section, or check out our YouTube channel to learn more.
Get a Quote for a New Combi Boiler Today
If you’re aiming to get the best deal on a new boiler, consider getting a quote from us, here’s why:
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