Best Combi Boiler Brands 2023 Re February 6, 2023

Best Combi Boiler Brands 2023

combi boiler in a kitchen

What are the best combi boiler brands?

This blog will be discussing the top 5 best combi boiler brands on the market, with help from the Which? Best Buy Survey results in 2021 and our good friend, Trustpilot. The Which? survey will help us when looking at brand reliability, customer score, engineer recommendation, ease of servicing and fixing and availability of spare parts.

This article will be focusing on the combi boiler brands as a whole rather than specific boilers. If you are looking for more information on the best combi boilers and best system boilers, we have blogs that cover these. We also have a blog on the best boilers to buy in 2023 which covers combi, system and conventional (regular) boilers.

So, what is a combi boiler?

A combi boiler combines a water heater and central heating into one single unit, removing the need for any additional hot water cylinders or cold water cisterns like you would need with a system or regular boiler. 

Combination boilers can also run on different fuels, meaning that they can also be installed in properties connected to the grid and off-grid homes.

How does a combi boiler work?

In simple terms, the water is supplied directly from the mains, a gas burner is ignited when the tap is turned on, the heat exchanger transfers the energy to the water which heats it up, ready for you to use. 

Worcester Bosch

Worcester Bosch boiler installation handoff

Worcester was formed in 1962 in Worcester, where it imaginatively took its name. It started off as a small engineering works before growing into the biggest boiler manufacturer in the UK It was acquired by Robert Bosch Holdings in 1992 to form the Worcester Bosch Group.

Worcester currently holds the Royal Warrant to supply heating to the Royal Family and has won the Which? Best Buy award for their range of boilers for the last ten years. This prestigious award is judged on reliability, build quality, recommendation, and customer score.

For a full timeline of Worcester Bosch’ history click here.

Worcester Bosch Which? Boiler Brand Survey

Here’s what Which? have to say about Worcester Bosch:

“Worcester Bosch is one of only two gas boiler brands to earn our Best Buy recommendation, thanks, in large part, to high owner satisfaction and recommendation. It’s boilers can be on the expensive side, but build quality is good and heating engineers praised the brand in general. The design of Worcester Bosch boilers can make them a bit difficult to repair, but you’re less likely to need a repair as Worcester Bosch boilers are very reliable.”

Worcester Bosch Trustpilot Reviews

Worcester Bosch has 91% above average scores on Trustpilot and mostly 5 out of 5 stars in the Which? survey, so the proof is in the pudding as they say. It is evident that Worcester Bosch as a brand, and their boilers particularly, are highly reliable and efficient, which is supported by their customer reviews. 

Here are only a couple of Worcester Bosch’s reviews on Trustpilot: 

“So impressed with the excellent service I received when I had a problem with my boiler, from my 1st phone call to report the problem to my boiler being fixed was a stress-free experience. Everything was dealt with quickly and efficiently and the problem was explained in easy to understand way. Thank you Bosch!”. 

“Had the boiler just under a year and it’s performed brilliantly, doing everything we’ve asked of it. Highly recommended.”.

Worcester Bosch is continuously praised for its high levels of customer service and aftercare. Besides having a brilliant range of combi boilers for all property sizes and demands, Worcester Bosch also offers between 5 to 12 years warranty on their combi boilers (dependent on the boiler model) for extra peace of mind. 

Rest assured, you will receive the same standard of customer service from us here at WarmZilla, which you probably already know. If you don’t, then click here to get a boiler quote in just 90 seconds, you won’t be disappointed!

When it comes to reliability, we can always count on Worcester Bosch to keep their customers in mind. Whilst the UK Government continues to increase the amount of green fuels being introduced, such as bio-methane and hydrogen, Worcester Bosch has ensured that their customers can be confident that their new gas boiler will run for its lifespan.

Martyn Bridges, Director of Technical Communication and Product Management at Worcester Bosch has said that all Worcester Bosch Greenstar condensing gas boilers manufactured since 2000 can accept a hydrogen blend of up to 20%.

Bridges also said that “the fact that Worcester’s boiler can already accept a blend of up to 20% is further evidence why injecting green fuels such as bio-methane and hydrogen into the UK gas grid is a positive step towards the wider implementation of these new, carbon-free fuels”.

Worcester Bosch is involved in multiple trials with hydrogen gas, including one at Keele University. For the last 18 months, Worcester Bosch has had 150 boilers that have been running up to a 20% hydrogen blend. They are now trialling this in 670 homes in Gateshead.

Worcester Bosch has continued to increase the use of green gases, launching the Hy4Heat programme that is currently trialling 100% hydrogen boilers that are running in specially-built demonstration houses in Northumberland.

More importantly, Worcester Bosch has made significant progress with prototypes and testing, developing hydrogen ready boilers. These hydrogen boilers look almost identical to your typical everyday gas boiler and they are installed in pretty much the same way.

Similar to gas boilers, hydrogen boilers will be connected to the gas mains and then the hydrogen or natural gases will be fed to the boiler from there. 

There are a few small differences when it comes to the internal components of the new hydrogen boilers, such as a hydrogen-ready flame detector and burner.

It is not possible to buy a 100% hydrogen-ready boiler just yet and until there is a reliable supply of hydrogen gas, it wouldn’t make much sense to have one yet anyway. But when hydrogen-ready boilers are ready for consumers to buy, Worcester Bosch are already on top form.



The Viessmann Group is a German manufacturer of heating, industrial, and refrigeration systems headquartered in Allendorf, Germany. (Wikipedia)

Viessmann’s roots go back even further than Worcester’s, starting in 1928, where Johann Viessmann was asked by a local gardener to build a boiler for his greenhouse. Johann, then a locksmith, thought ‘why not’ (they didn’t have Playstations back then).

Viessmann innovated on the iron boilers around at the time and built his using steel which heated up faster and used less fuel. Nice work Johann! Soon, all the gardeners in the village wanted one, and Johann got his model patented and set to work. 

Since January 2018, the company is led by Martin Viessmann (Chairman of the Executive Board), Maximilian Viessmann (Co-CEO and part-time Bond villain), and Joachim Janssen (Co-CEO). Making Viessmann a family-owned business for four generations, quite a rare thing.

You can find out more about the Viessmann company and the rich history of over 100 years in business yourself, as that could be a blog on its own.

Viessmann Which? Boiler Brand Survey

Results show that Viessmann as a company is seen as a reliable and good quality brand for boilers. Although they lack slightly in the availability of spares and parts category, which can become a problem during installation or future servicing. 

Here’s what Which? have to say about Viessmann:

“With a high proportion of satisfied owners and being well-liked by heating engineers, Veissmann boilers are a great Best Buy. These boilers are reliable, and a number of heating engineers in our survey mentioned good build quality. The only minor drawback is that sourcing replacement parts can be a little slow.”

Viessman Trustpilot Reviews

Although Viessmann UK only has 2.4k reviews, over 89% of those are above average on Trustpilot. Viessmann are confident in the reliability of their boilers, which is why they come with warranties of up to 10 years.

Here are what customers have to say about Viessmann boilers:

“Excellent product and does what it says on the tin.”

“I was extremely happy with the installation and the product is magnificent.”

Viessmann has 18 different combi boilers to choose from, ranging from 19kW to 35kW, meaning that there is a combi boiler for everyone. 


Vaillant in blue and white kitchen

Before we get into the nitty-gritty of customer reviews and brand performance, let’s talk a little about the history behind Vaillant as a brand.

Vaillant was formed way back in 1874 by Johann Vaillant in Remscheid, Germany. Johann Vaillant, the tenth child in his family, founded his own workshop as a copper beater and pump maker.

Many inventions have been credited to Vaillant over the years including modern-day central heating in 1924. Previously each room was heated individually by stoves or fireplaces until Vaillant introduced the central heating boiler that could heat multiple radiators simultaneously – revolutionising home heating.

The Vaillant boiler range has been given a Which? Best Buy award and they have also been awarded a Quiet Mark Accreditation, from the Noise Abatement Society for their quiet running boilers.

For a full timeline of the Vaillant, company history click here.

Now, let’s get into the juicy bit. Let’s see what customers really think about Vaillant boilers. 

Vaillant were rewarded the best overall score in the Which? Best Boiler Brand survey 2020.

Vaillant Which? Boiler Brand Survey

The survey results speak for themselves when it comes to Vaillant boilers. Again, another great, highly reliable and efficient combi boiler brand. 

Here’s what Which? have to say about Vaillant:

“Vaillant boilers were a Best Buy in 2020 and are highly regarded by heating engineers who say they’re good quality and easy to work on and source parts for. However, they’re not entirely without problems and Vaillant’s lower customer score this year means it’s no longer a Best Buy.”

Vaillant Trustpilot Reviews

Vaillant has a rating of 4.6 out of 5 stars on Trustpilot from over 15k reviews. With over 90% of Vaillant’s reviews being above average, customers can be confident that they are dealing with a reliable and efficient boiler brand that cares about its customers. 

Here are some Trustpilot reviews to support this statement:

“I had a brand new Vaillant EcoTec Pro installed recently and I love it, could not ask for better with both the boiler and WarmZilla who I purchased it from. Great service and a great boiler, I’m so glad I have hot water again, I’m just waiting on receiving my guarantee paperwork, I’m really really happy with everything”

“I’m really pleased with my new Vaillant, it’s very quiet and easy to use. Would highly recommend.”

Similarly to Worcester Bosch, Vaillant’s reviews not only show how satisfied customers are with their boilers but also with their customer service.

Vaillant boilers have warranties of 2-7 years depending on the model and whether certain terms are met, which is pretty good. However, with WarmZilla, when buying a new or replacement combi boiler, we offer up to 10 years guarantee on all combi boilers.

To get a quote in minutes, click here. 


Baxi Boiler

Founder Richard Baxendale opened the doors to his new company in 1866. By 1955, Baxi became a household name for heating. The Bermuda, Baxi’s most famous gas-fired boiler was launched in 1966, the same year in which Baxi celebrated 100 years in business. For more information on Baxi history, you can click here. 

Baxi state on their website: 

“Our aim is to deliver best value through reliable, energy efficient products and high-quality service and technical support, while promoting environmental, social and economic sustainability.”

Baxi’s Which? Best Boiler Brand Survey

Here’s what Which? have to say about Baxi:

“Baxi is one of only three brands to earn five stars for ease of servicing. Parts availability is good and reliability is excellent. Baxi narrowly misses out on our Best Buy recommendation: engineers aren’t quite as emphatic about build quality and the brand achieves a slightly lower customer score than the very best gas boiler brands in our survey.”

BAXI Trutpilot Reviews

Baxi has over 4.5 stars on Trustpilot and over 35k reviews. Over 86% of Baxi’s reviews are above average, showing that these are again, another great boiler brand. Baxi has won many awards including Gas Industry Award in 2017, for both customer service and energy efficiency. 

Here are some customer reviews:

“The engineer did an excellent job, going above and beyond in terms of service. The boiler was just meant to undergo a service but I had a problem with it resulting in no heating, which the engineer kindly sorted. Moreover, the engineer kindly informed me how to use the heating system efficiently. The engineer was in general very helpful and friendly and gave excellent service.”

“Fantastic, thorough, friendly service today. Went above and beyond to talk me through each step furthering my understanding of my boiler and system. Came on time and left the place tidy. Thank you very much.”

Many Baxi boilers now come with a warranty of between 7 and 10 years, which is an extensive period of time, so that you don’t have to worry about any occurring costs for repair or servicing for a while. 

Although WarmZilla does not currently sell Baxi boilers, we recommend Baxi boilers as another trusty combi boiler brand.



Ideal boilers were founded in 1905, giving them over 100 years of experience in delivering boilers to homes throughout the UK.

Ideal is one of the pioneers in bringing high-efficiency boilers to market and they continue to bring reliable, efficient boilers to market to this day. 

One of the first modern-day boilers was brought to market by Ideal in 1920 and known as the Cookanheat. The Cookanheat was a freestanding stove that combined an open fire, central heating boiler, cooking oven, and hot cupboard.

Ideal has come a long way from the Cookanheat, offering a range of combi boilers that offer high efficiency at a very reasonable price.

For more information on Ideal’s brand historyclick here. 

Ideal Boilers’ Which? Best Boiler Brand Survey

Here’s what Which? have to say about Ideal:

“The feedback from heating engineers about Ideal boilers is generally positive. They’re keenly priced and viewed as suiting landlords and those on a budget, but there can be problems with lower-quality parts. Few Ideal boiler owners in our survey have experienced any issues though, and Ideal sits in the top half of the boiler brands we’ve reviewed.”

Ideal Trustpilot Reviews

93% of Ideal’s Trustpilot reviews are above average, 87% of these being ‘excellent’ reviews. 

Here are a couple of customer reviews:

“Ideal great customer service and excellent knowledge. Would highly recommend them.”

“Everything was completed in a very professional way. Excellent service.”

From looking at Ideal’s Trustpilot reviews, the majority discusses the installation process rather than the company’s customer service or aftercare. However, we can see from the Which? survey that Ideal boilers are becoming a high contender for one of the best combi boiler brands on the market. 

After the installation of your new boiler you want to know that you’ll be covered by the manufacturer in the unlikely event of an issue. Ideal offers extensive warranties of up to 10 years on some of their boilers to see that you’re well covered. However, some may worry that a few Ideal combi boilers only have 2 years warranty, but worry not! When purchasing with WarmZilla, you will get an 8 year guarantee on all boilers. 

The cost of new boiler could vary from one brand to another, so take our boiler survey to get a boiler package that suits your house and wallet!

Overall review - the best combi boiler brands

We’ve put together the below summary of the best combi boiler brands rating. 

BrandOverall ScoreReliability ScoreBrand Customer ScoreBrand Engineer Overall ScorePrice for a 30kW Combi
Worcester Bosch84%5 stars5 stars4 stars£800-£2,460
Viessmann81%5 stars5 stars4 stars£780-£1,280
Vaillant76%4 stars4 stars5 stars£1,160-£1,410
BAXI76%5 stars4 stars4 stars£880-£1,000
 Ideal74%5 stars4 stars4 stars£590-£1,270
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