Viessmann Vs. Worcester Bosch Vs. Vaillant Re February 22, 2023

Viessmann Vs. Worcester Bosch Vs. Vaillant


When you enter the world of boilers, you will often hear about Viessmann, Worcester Bosch, and Vaillant. These are the premium boiler brands on the market, offering a range of highly reliable and efficient boilers. 

If you are looking for a more cost-efficient boiler brand, there are other ‘budget’ boiler brands available such as Vokera and Ideal boilers. We have compared cheaper boiler brands in other blogs, such as Ideal Vs Glow-wormIdeal Vs Baxi/Potterton/Main, and Ideal Vs Alpha, for those looking for a more cost-friendly boiler. 

If you would like more information about the cheapest combi boiler brands or boiler models, the cheapest system boilers, or the cheapest regular boilers, we have separate blogs that cover these. Once you’ve finished reading this blog, click these links to head over and read more of our blogs 😊

If you are still unsure which boiler brand or model to choose from once you’ve finished this blog, then why not try out our Boiler Comparison Tool. This brand new tool allows you to compare up to three boiler models or brands at one time, to help you find the perfect boiler for you.

You can also do our 90-second survey that asks you a set of questions about your current central heating system and what you are looking for in your boiler and then gives you a list of boilers ideal for your home and needs! Get your quote now.

This blog will discuss selected combi boilers from each brand so that we can compare each boiler and see which brand is our overall winner. We will be comparing factors such as efficiency ratings, warranty lengths, dimensions, and price.

We have already covered a Vaillant vs Viessmann blog, as well as a Worcester Bosch vs Viessmann blog if you would like to read over them.

The combi boilers we will be discussing throughout this blog are:

Viessmann History

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 Bosch’s, starting in 1928, where Johann Viessmann was asked by a local gardener to build a boiler for his greenhouse. 

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 is 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.

Worcester Bosch History

Worcester was formed in 1962 in Worcester, where it imaginatively took its name. It started 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.

Whilst the UK Government continues to increase the amount of green fuels being introduced, such as bio-methane and hydrogen, Worcester Bosch 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.

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

Vaillant History

Vaillant was formed way back in 1874 by Johann Vaillant in Remscheid, Germany. Johann Vaillant 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

To help us decide our final winner, let’s take a look at how each brand has been rated in the Which? Best Boiler Brand Survey in 2021 to see what customers think of these brands. 

During the Which? Best Boiler Survey this year, more than 8,000 members of the public were asked to rate their boiler brand on their boiler’s reliability and whether or not they would recommend their boiler brand to friends or family. 

Out of the 16 boiler brands included in the survey, Worcester Bosch was ranked first place, Viessmann ranked second place and Vaillant came in at third place. This supports our claim that these boilers are three of the best boiler brands on the market.

Each boiler brand was reviewed on:

  • Reliability
  • Brand Customer Score
    These scores are based on the survey response taken from the May/June Which? Best Boiler Brand Survey.
  • Brand Engineer Overall Score
    These scores are based on the response from 153 Which? Trusted Traders when asked to score each boiler brand on their ease of servicing, ease of fixing a common fault and availability of spares and parts.

Here are the scores for each brand:

 ViessmannWorcester BoschVaillant
Overall Score81%84%76%
Reliability Score5 stars5 stars4 stars
Brand Customer Score 5 stars5 stars4 stars
Brand Engineer Overall Score4 stars4 stars5 stars

Looking at these scores supports our claim that Viessmann, Worcester Bosch, and Vaillant are three of the most reliable boiler brands.

Worcester Bosch smashes it out of the park once again, awarded first place out of the 16 brands that were reviewed, with an overall brand score of 84%. Viessmann came second, scoring an overall brand score of 81% and Vaillant came in at third place, with 76%. 

Now we know a little bit of each brand’s history and what their customers think of their brands, let’s compare a combi boiler from each boiler brand to help us decide which one will be our overall winner.

Combi Boiler Comparison Table


Viessmann Vitodens 050-W 29kW 

Worcester Bosch Greenstar 4000 30kW Vaillant EcoTec Pro 30kW 
Flow Rate12 l/min12.3 l/min12.3 l/min
DHW kW Output 29kW30kW30kW
CH kW Output24kW24kW25kW
ErP Rating AAA
Warranty3 years*10 years10 years
Efficiency Rating 93%94%93%
Dimensions (mm)H:707 x W:400 x D:350H:724 x W:400 x D: 310 H:720 x W:440 x D:335
Price** (inc VAT)£1,889.00£1,969.00£1,989.00

Straight off the bat, we can see that all three boilers are very similar in what they offer and their performance. To ensure that the comparison is fair, we have chosen boiler models with similar, if not the same kW outputs for central heating and hot water. For this blog, we are focusing on boilers with an output of around 30kW. 

Thanks to these outputs, these boilers would be ideal for homes with up to 20 radiators and 2 bathrooms. 

Combi boilers are ideal for homes with limited space. This is because they are designed and built to have the central heating system and water heater combined in one unit, saving space in your home. As a result of its clever design, combi boilers remove the need for any additional hot or cold water tanks, unlike what you would need for a system or regular boiler. 

When comparing these three combi boilers, we can see that they all have a similar efficiency rating of between 93% and 94%, making them A-Rated boilers. What does efficiency rating mean? Well, the higher the rating, the more efficient your combi boiler is. If your combi boiler has an efficiency of 93%, this means that only 7% of the gases being used when your central heating system is turned on, is being wasted. 

In financial terms, this means that for every £1 you spend on your central heating, only 7p of it is being wasted. This is why we recommend that when you are looking to purchase a new or replacement combi boiler, that you do your research into the boiler’s efficiency rating because cheaper boilers can often be a lot less efficient, costing you more money on your energy bills, in the long run. 

One of the more noticeable differences is the warranty lengths. We can see from the table that the Viessmann Vitodens 050-W 29kW comes with a standard 3-year manufacturer’s warranty, which is significantly less than the warranty that the Worcester Bosch Greenstar 4000 30kW and the Vaillant EcoTec Pro 30kW come with. 

On that note, this is a great time to mention that when you purchase a new or replacement Viessmann Vitodens 050-W boiler with WarmZilla, you will receive a standard 10-year warranty. How about that for extra peace of mind eh?

It’s difficult to compare three boilers that are all classed as very robust, efficient, and reliable boilers, which is why they are three of the best-selling boiler brands on the market.

The prices vary slightly for all three combi boilers, which is the factor we will consider to choose our final winner. These prices are from our website and are based on a 3-bedroom semi-detached home with one main bathroom and no additional shower rooms. 

Did you know that when you buy a new boiler with WarmZilla, you don’t just get the boiler alone? We have listed below everything that your boiler package includes:

  • Flue Kit
  • Neomitis RF Digital Wireless Room Thermostat
  • System Cleanse of your current central heating system
  • Magnetic System Filter for ongoing protection
  • Chemical Inhibitor for extra protection for your new boiler
  • Free removal of your old central heating system
  • Installation by a Gas Safe Engineer

Here are our final thoughts on which brand is the winner and why. 

Vaillant comes in at 3rd place. This is because it is the most expensive boiler model of the three. The Vaillant EcoTec Pro 30kW is £20 more expensive than the Worcester Bosch, although it has a lesser efficiency rating of 93%. 

In second place, is the Viessmann Vitodens 050-W 29kW. We have awarded the 050-W second place because of its warranty length. Although you would receive a 10-year warranty with WarmZilla, customers who may have bought elsewhere would have only received the standard 3-year warranty on this boiler. It also has the lowest flow rate of all three boilers. 

This means that our winner in the battle between Viessmann, Worcester Bosch, and Vaillant is…


Worcester Bosch!

Worcester Bosch is known for producing fantastic products that are compatible with different wireless controls. They are also known for their fantastic customer service and aftercare. 

For this total cost of £1,969.00, you will be given a 10-year standard warranty, a reliable boiler with an efficiency of 94%, helping you save money on your energy bills, a brand new, sleek, modern boiler model that will satisfy your homes needs for many years to come. 

On this note, Worcester Bosch has just been awarded a Which? Best Buy endorsement for the 12th year running, with its gas and oil boiler ranges being top-rated in the industry.

WB 8000

How much does it cost to install a boiler?

There are a lot of factors that contribute to what price you will pay to get a new boiler installed but this guide will explain all of the factors and give you example prices so you’ll know exactly how much you can expect to pay.

When having your new boiler installed, you will have to consider factors such as moving your boiler. Moving your boiler’s location can cost on average, between £400 and £900.

The final cost will depend on how far your boiler needs to be moved and the type of boiler you are having installed. You may need additional parts for your new boiler, for example, if you move the boiler from a location where the flue terminates horizontally from the boiler through a kitchen wall, to an attic where the flue will need to be changed to a vertical flue, additional costs for parts will be incurred. 

At WarmZilla we charge £150 to move your boiler within the same room, £300 for other rooms, and £500 to move your boiler into the loft. 

Other factors that may affect the final cost include:

  • Pipework upgrade
    Most people wouldn’t hear about this until their installer was informing them that they were going to need to pay an extra fee to upgrade their pipework. Not with WarmZilla. The price we quote you is fixed. If we need to upgrade the pipework then it won’t cost you any more.
  • Powerflush / System Cleanse
  • System Filter
    Supply and fit of a magnetic filter will cost you anywhere between £120 – £250 depending on the brand and installer. Again, with WarmZilla, there is no charge, we include a system filter as standard with every boiler we install.
  • Plume Kit
    As ever, the cost of the plume kit is included in your WarmZilla fixed price boiler quote. It will automatically be included in your order if the answers to the survey indicate that it’s necessary.
  • Labour and Installation Costs
  • Smart thermostat or added controls
    With every boiler installation, WarmZilla includes a Neomitis Thermostat as standard, it’s not as advanced as a smart thermostat such as the Google Nest but you can upgrade to a Nest if the extra gadgetry is what you want in your life.

If you want a more in-depth guide to how much it costs to install a boiler, we have a separate blog that covers this.

How to ensure you choose the perfect boiler

  • Ensure that you choose the correct boiler type for your home 
  • Ensure that you choose the correct kW output boiler model for your home
  • Choose a boiler with has an A-rated efficiency rating
  • Look at the dimensions of the boiler to ensure that it fits the space it will be installed
  • Take warranty into consideration 
  • Compare boiler prices – remember that cheaper boilers are not always the best option

** Please note that prices were correct on the date of publication. Prices are subject to change.

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