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Worcester Bosch Vs Viessmann Boilers

Worcester Bosch vs Viessmann boilers

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Worcester Bosch Boilers Review

Our heating engineering team at Warma have been installing boilers for decades and they say that Worcester Bosch boilers build quality are among the best. Throughout their boiler range they offer a 5 year warranty as standard. Worcester Bosch claim that one out of every ten boilers installed in properties across the UK, are theirs.

Some of the features of the Worcester Bosch boilers include them being a well known brand within the UK, who boast a lot of satisfied customers. Their boilers come with simple controls that clearly display information to their end users in a manner that is easy to understand and most importantly, use. Worcester Bosch boilers have a very low risk of their condensate pipe freezing in severe weather. Below are a list of other features of the range of Worcester Bosch boilers: –

  • Wide choice of controls enables greater comfort and economy.
  • Low energy pumps reduce electrical usage.
  • Instantaneous hot water, always available.
  • Achieves an A+ ErP package efficiency rating for heating when installed with a Wave smart internet connected control.
  • High hot water flow rate.
  • Simple boiler control knobs with clear temperature display.
  • Frost protection is included, reducing frost risk if installed in a garage or a loft.
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Viessmann Combi Boilers Review

Viessmann were world leaders in commercial heating boilers long before they entered the domestic boiler market. Their commercial heating boilers keep some of the largest buildings in the world warm throughout the winter months; these buildings include stadiums and factories. 

Viessmann are a boiler brand that continue to innovate and this is evident through their extensive boiler range. All viessmann boilers are able to extract all of the heat contained in the flue gases and this allows their boilers to convert this back into heating energy. This is possible through their boilers condensing the gases into water vapour. This innovation in their boiler range would be wasted on older non-condensing boilers.

All boiler manufacturers in the UK have a range of condensing boilers so this isn’t something unique to Viessman although their boilers are highly reviewed and are said to be at the very top of the market. 

Viessmann combi boilers have some top of the range features, these include a high quality stainless steel inox radial heat exchanger, long term reliability and high energy efficiency with a 98% efficiency rating on the vitodens 200-W. The Viessmann brand also boasts having some of the quietest boilers in the UK and available in a range of compact designs and low weights. If viessmann boilers are installed by an approved Viessmann installer then they have an extended 10 year warranty available. 

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What Do We Recommend?

When it comes to the quality of a boiler there is one component that can trump the rest and that is the heat exchanger. Viessmann boilers have their own patented stainless steel inox radial heat exchanger. This is unique to the Viessmann boiler range whilst many other boiler manufacturers including Worcester Bosch use an aluminium heat exchanger and in most cases is sourced by a third party manufacturer. 

patented stainless steel inox radial heat exchanger
patented stainless steel inox radial heat exchanger

In the review of the best type of boilers between Viessmann and Worcester Bosch it is important to note that the use of a stainless steel heat exchanger as is the case in Viessmann means that it is highly resistant to corrosion in a wide range of pH levels. In the case of Worcester Bosch using aluminium as the core material for this integral part can cause the heat exchanger to corrode much faster. 

Stainless steel heat exchangers also do not require the use of special fluids to narrow the pH levels as is the case with a boiler that uses an aluminium heat exchanger, something which all homeowners should make a note of. 

A big thumbs down for Worcester Bosch is that if the heat exchanger is damaged through the improper use of these fluids then this can void your warranty completely, something which owners of a Viessmann boiler need not worry.

Stainless steel is a much more expensive material to source than aluminium which is why most boiler manufacturers tend to use aluminium but that does bring with it, some reliability issues. Whilst aluminium means that the boiler can remain lightweight and will benefit from a better thermal conductivity, stainless steel over the long run will work out much better value for money for the end consumer. This is due to the fact that aluminium will corrode and break down long before stainless steel. A boiler with a quality stainless steel heat exchanger will increase the life of the boiler and will mean less chance of a breakdown or maintenance call outs.

We thought it would be a good idea to show our readers the difference in the overall lifespan of an aluminium heat exchanger compared to a stainless steel heat exchanger.

Heat exchanger performance analysis

As you can see from the diagram above, the longevity of the boiler’s integral parts becomes a sticking point for the choice between a Worcester Bosch boiler vs a Viessmann boiler. 

A heat exchanger that has the ability to last much longer means that you save money in the long term by removing the need for having to replace this part much sooner than a heat exchanger made from an inferior metal.

The stainless steel heat exchanger inside the Viessmann boilers will last much longer without losing efficiency.


Warranties are a big deal for boiler manufacturers and is a big selling point for any homeowner looking to install a new boiler in their property. Worcester Bosch and Viessmann both provide warranties with any purchase of a new boiler.

Worcester Bosch gives you 5 years standard warranty with any new boiler, however, Viessmann beats that by offering anywhere from 7 to 10 years warranty and they also offer a number of discounts if you get the boiler installed by an approved installer.

With that in mind, the Viessmann boiler can offer nearly double the warranty time compared to a Worcester Bosch and as we have discovered, the technology and energy efficiency is far superior.

Final Thoughts

At Warma UK our expert heating engineers would recommend the Viessmann range of boilers over the Worcester Bosch range of boilers – if you do not have a top ceiling budget and can afford to go for a premium option then this would be the ideal choice. Their superior heat exchanger and the longer warranty means that the higher purchase price you pay now could pay off in the long term.

With that being said Worcester Bosch boilers are very good quality and still have great reviews. If you are on a budget but still want a boiler which is renowned for great reviews then this range of boiler would be an ideal fit for your home.

Michael Cornish