07th February, 2022

Worcester Bosch Vs Viessmann Boilers

Which boiler will come out the winner between these two powerhouse boiler manufactures!

Worcester Bosch Vs Viessmann Boilers

When choosing a new boiler, it can be hard to decide which brand to go for when they all seem to be offering the same promises in regards to reliability, durability and efficiency. Our top two bestselling boiler brands at iHeat are Worcester Bosch and Viessmann.

An Introduction to Worcester Bosch

Founded in 1962, Worcester Bosch is probably the most well-known boiler brand. Their bestselling model, the Greenstar i, can be found in over one million UK homes and as the eleven time winner of Which? Best Buy it’s clear Worcester Bosch are a promising and popular brand and take a strong position amongst our best combi boilers.

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An Introduction to Viessmann

Viessmann is a family-owned company that was founded in 1917 by Johann Viessmann and has since grown very popular in Germany and the rest of Europe, becoming leaders in the commercial heating space long before they entered the UK domestic market.

However, in more recent years, Viessmann boilers have started to appear in more and more UK homes as their advanced German engineering and innovation became more well-recognised.

When comparing these two boiler brands, we’ll be taking a look at four main points and comparing two of their most popular boilers, the Worcester Bosch Greenstar 8000 Style 30kW and the Viessmann Vitodens 050-W 29kW.

The four factors we'll be taking into account for this comparison are as follows:

  • Energy Efficiency
  • Technology
  • Price
  • Warranties

Worcester Bosch

Energy Efficiency

The Greenstar 8000 Style 30kW offers an amazing efficiency percentage of 94% and has a hot water flow rate of up to 10.7 litres of hot water per minute, making it one of the most efficient A-rated boilers.


The Greenstar 8000 Style boiler is packed with innovative new features which keep it performing at its best. Developed to suit virtually any domestic heating requirement, this is Worcester Bosch’s most powerful and connected wall hung boiler yet. With an easy to use, full colour display and connectivity, with the Bosch EasyControl app, you can control your home’s heating and hot water from anywhere, helping to keep costs down.

Unfortunately, their decision to keep the aluminium heat exchanger makes them drop below Viessmann, who use a stainless steel heat exchanger. The problem with aluminium exchangers is that they corrode easily and are less reliable, becoming clogged easily.


You can purchase a Worcester Greenstar 8000 Style for £2,395 including installation with iHeat. These boilers are at the higher end of the price range so you may be wondering why you should pay extra than other well known brands and if they are really worth it. The truth is, you’re paying for its guaranteed reliability, high efficiency and super sleek style.

Whilst it is possible to find cheaper boilers, they won’t be as reliable or long-lasting as a Greenstar Style 8000, costing you more in repairs and replacements in the long run. The average lifespan of a combi boiler is between 10-15 years, whereas a Worcester Bosch tends to last longer, between 16-20 years.


If our word on how great these boilers are isn’t enough, you can rest assured with 10 years guarantee on a brand new Worcester Greenstar 8000 Style when installed with iHeat.*


Energy Efficiency

This exceptional Vitodens 050-W definitely comes out on top as the most efficient boiler with an A rating and up to 97% efficiency. This boiler will seriously cut fuel costs whilst being incredibly reliable and offering the highest quality with its new stainless steel heat exchanger, making it extra robust whilst consuming relatively little natural gas. An exceptionally quiet operation means you won’t even notice as it works hard to provide you with heating, instantaneous hot water and an impressive hot water flow rate of 12.4 litres/min.


Viessmann uses Inox, the highest grade of stainless steel, which they manufacture exclusively in-house, making it incredibly reliable and less likely to get clogged or corrode. It also doesn’t require special fluids in the same way aluminium heat exchangers do and are compatible with clean water. This decreases the chances of damaging it, therefore increasing it’s chances of a longer lifespan.

This combi boiler will also integrate into any home with compact dimensions (707x400x350mm) and low weight (37kg), without compromising quality. With its easy to use LCD display and interface, you can control your heating to match your lifestyle and preferences.


Although the Viessmann Vitodens 050-W is cheaper than the Worcester Greenstar Style 8000 at £2,060 (including installation), you certainly won’t be compromising on quality. If this still seems expensive compared to other boilers, remember that Viessmann manufacture their stainless steel heat exchangers in house which is more expensive than sourcing cheaper aluminium from third parties. So whilst you are paying more, it is definitely worth it to ensure a longer boiler lifespan.


Still unsure about the reliability of a Viessmann? To ensure you get your money’s worth, you will receive a 10 year warranty on a Viessmann 050-W 29kW when installed with iHeat.*

So which should you choose?

Despite Worcester Bosch being the most popular boiler brand in the UK, Viessmann takes the lead here, surpassing Worcester in almost all aspects. The Vitodens 050-W is more energy efficient than the Greenstar Style 8000, with its 97% efficiency and an impressive hot water flow rate of 12.4l/min, compared with Worcester’s 84% efficiency and 10.7l/min hot water flow.

Viessmann’s technology is also far more superior with their Inox heat exchangers that are a greater value for money than Worcester’s aluminium which are more likely to corrode, warp and break down. Despite these heat exchangers being more expensive to manufacture, the Vitodens is still more affordable than the Greenstar Style 8000, once again putting it on top.

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One advantage the Greenstar Style 8000 does have over the Vitodens 050-W is it’s appearance. Available in black or white with a sleek and expensive looking finish, this is an attractive boiler.

With iHeat, the warranties are the same, so no matter which you decide to purchase, you will be guaranteed a high quality boiler that lasts at least 10 years.* Get a free, fixed quote on a new Worcester Bosch or Viessmann boiler today.

*Boilers must be serviced annually by a Gas Safe Registered engineer.

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