Viessmann and Vaillant are two of the best German boiler manufacturers offering their products in the UK today.
While Vaillant is the better-known brand in the UK out of the two, Viessmann has brought their commercial heating experience to their domestic boiler range and have won the Which? Best Buy awards for several years in a row.
Viessmann is one of the leading international manufacturers of heating systems, and have rapidly become the boiler of choice around the world, for reasons you’ll see later in the post. Viessmann, founded in 1917, now has over 12,000 employees across the world. They are truly international with a presence in 12 countries with 23 production divisions, subsidiaries and representations in 74 countries, and 120 sales offices around the world.
Viessmann has also been awarded a multitude of awards over the course of its history. Recent awards include:
Red Dot Award: Product Design.
Trophée des Usines.
iF product design award.
Number 1 Trade Partner.
Good Practice Energy Efficiency.
Commercial Heating Experience and Best Buy Award
What a lot of people don’t know is that Viessmann is a world leader in the commercial heating space. They are also number 1 in Europe for the same category. Several large buildings around the world run on Viessmann’s commercial boilers. These include stadiums such as the Principality Stadium in Cardiff, corporate headquarters, and large factories.
That commercial heating experience segues very nicely into the domestic sector, resulting in powerful, high-efficiency boilers, all of them winning the coveted Best Buy UK award from a prominent consumer research magazine.
Past Complaints and Myths
While Viessmann’s foray into the UK domestic boiler market has been comparatively recent in 1989, compared to rival boiler manufacturers, they have caught up at blazing speed.
Any complaints about the non-availability of spare parts are now ancient and irrelevant, as Viessmann have made sure to address those.
Their UK headquarters are at Telford, and all the spare parts are stocked at Plumbases around the UK and other plumbing merchants. Plus an extensive network of engineers means a Viessmann engineer can be at your doorstep within 24-48 hours to resolve any boiler issues, which rarely happens because these boilers are so reliable.
Viessmann’s current product range includes gas, oil, steam and biomass boilers, hot water cylinders, combined heat and power generation, photovoltaics, air and ground source heat pumps, refrigeration cabinets, coldrooms and biogas plants.
About Vaillant UK
Along with Worcester Bosch, Vaillant have been market leaders in the UK for a long time, and have created front-running products in the industry. From water heaters in the 1900s, to the combi boiler about 30 years ago. In the renewable technology space, Vaillant are developing systems which utilise sustainable energy sources. Vaillant products consistently get high energy efficiency ratings and low emissions, and have a great reputation for performance, quality and reliability. They also own the Glow-Worm boiler brand in the UK.
Vaillant are present in over 20 countries with exports to more than 60 states. They are an international family-owned company. They are the second-largest European manufacturer in the heating technologies sector. In addition, Vaillant are also active in the ventilation and air-conditioning technology markets.
New and Innovative Boiler Models
The company develops and manufactures its products and services at sites in the UK, Germany, France, Spain, Italy, Slovakia, Turkey and China.
Much like Viessmann, they have ventured into the storage combi boiler space as well with their ecoTEC Plus Combination Store model, which is a combi boiler with a water tank.
Viessmann vs Vaillant: Comparison & Review
Before we start, let us point out that both Viessmann and Vaillant make excellent boilers. You will get many years’ worth of efficient home heating and consistent hot water with both Viessmann and Vaillant. Having said that, a new boiler purchase is one of the most important buying decisions a homeowner can make. And so, you want to be extra careful in choosing the best boiler.
Because you don’t change boilers every year, whichever boiler you choose will have to last you at least between 10-20 years.
Below is a comparison chart for competing 35 KW boilers from both Viessmann and Vaillant. Specs are almost the same, except for some minor differences and one major difference when it comes to warranty. We hope the following review will help you make a more educated buying decision and make it easier for you to choose between Viessmann and Vaillant boilers.
Please note that the prices given below are for boilers only. The final price for a boiler installation will include labour costs, extras like chemical flush, magnetic and limescale filters, and thermostats etc. For similar output of 35 KW, below is the price (boiler only) for the two competing models:
For the exact same output of 30 KW, the Viessmann boiler is a whopping £389 cheaper!
Your obvious next question will be “Why is the supposed better boiler cheaper?” I mean isn’t stainless steel more expensive to source than aluminium?
As we mentioned above, because of Viessmann’s experience in the commercial heating space, and the fact that they manufacture most of their patented components in-house, they can compete at the same price point as their rivals.
Also, the fact that Viessmann’s rival boiler brands source internal components from a third-party provider, factors into the overall cost. What’s even more surprising in all this is the fact that Viessmann is technically a superior boiler!
Conclusion – Viessmann is more affordable.
Viessmann Warranty – 7 Years Parts and Labour/10 Years on Stainless Steel Heat Exchanger*
Vaillant Warranty – 5 Years (Standard warranty)
*Extended warranty when installed by a Premium Partner like Boilerhut
Viessmann is comfortable offering 10-year warranties on their stainless steel heat exchanger because they are confident in its reliability and durability.
Vaillant offers a 5-year standard warranty on their boilers. To get extended 10-year warranties, you’ll need a Vaillant Advance Installer, and for the boiler to be installed with a Vaillant Boiler Protection Kit and registered on Advance.
Conclusion: Viessmann edges it when it comes to warranty.
Technology and Reliability
The internal working components of a boiler have to operate in extreme environments inside a boiler, tolerating ridiculous thermal and mechanical stress, various types of system water qualities and dissolved oxygen. They also have to tolerate the effects of corrosive condensate. This is why it’s crucial that the boiler manufacturer uses materials that are specifically designed to withstand inhospitable environments. One such component is the heat exchanger.
Boiler manufacturers use two types of heat exchangers: aluminium and stainless steel.
Stainless steel is vastly superior to aluminium when it comes to withstanding extreme temperatures, and resistance to corrosion. The majority of the boiler manufacturers in the UK use an aluminium heat exchanger, except a handful who use a stainless steel heat exchanger. Viessmann is one of that handful.
The Inox-Radial stainless steel heat exchanger used in Viessmann boilers
Viessmann has pioneered the Inox radial stainless steel heat exchanger, and pretty much the best, highest quality heat exchanger in the market right now. This helps Viessmann achieve the highest efficiency of 90% among its competitors, going as high as even 98% efficiency on some higher-end models like the 200-W.
Stainless steel heat exchangers have become the preferred option to deliver long term efficiency and reliability. And for condensing boilers, a stainless steel heat exchanger can last up to 5-7 years longer than one with an aluminium heat exchanger. The grade of stainless steel used in a heat exchanger must also be highly resistant to corrosion, internally, and externally so that the component retains its efficiency throughout the boiler’s operating life.
Below is a comparison of the lifespan of a stainless steel heat exchanger (in blue) vs an aluminium heat exchanger (in red).
Viessmann – Built-in Shock Arrester – Reduce Water Hammer
If you haven’t come across what’s called a “water hammer”, you’re lucky. If you don’t know what that is, it’s the loud rattling of your water pipes every time you open a tap in your house. A water hammer is a pressure surge or wave caused when a fluid (usually a liquid but sometimes also a gas) in motion is forced to stop or change direction suddenly (momentum change). A water hammer commonly occurs when a valve closes suddenly at an end of a pipeline system, and a pressure wave propagates in the pipe. It is also called hydraulic shock.
This pressure wave can cause major problems, from noise and vibration to pipe collapse. It is possible to reduce the effects of the water hammer pulses with accumulators, expansion tanks, surge tanks, blowoff valves, and other features.
Viessmann’s built shock arresters right into their boilers, reducing, limiting, or even avoiding the water hammer problem altogether. Anybody who’s experienced a water hammer problem knows what a nuisance it is. Basically, it’s like someone hammering your walls every time someone opens a tap in your house. Even more enjoyable when someone in your house is taking a shower at 6 am on your weekend off.
Conclusion: Viessmann is the clear winner here.
Ease of Installation
It’s easier to install Viessmann boilers because of two main factors.
Viessmann boilers are more compact, as you can see in the comparison chart above. Even if the difference is small, sometimes it can make all the difference.
The condensate and pressure relief pipe is combined inside a Viessmann boiler, which makes it easier to cite the boiler.
Final Verdict, Thoughts and Summary
Viessmann and Vaillant both offer solid boilers. Both are A-rated by the EPC register. But there has to be a winner, and with our experience of boiler installation of over 40 years, plus keeping recent installations, reviews and complaints in mind, Viessmann is the clear winner because of the following reasons:
Viessmann is cheaper by £400-£500 for the same capacity boilers
Viessmann is slightly more efficient. Up to 98% efficient on select models
Viessmann offers 7-10 years warranty through an approved installer like Boilerhut
Viessmann boilers are technologically superior and use Inox-radial stainless steel heat exchangers. Which also makes them more reliable
Because Viessmann are more compact, and because the condensate and pressure relief pipe is combined, it is easier to cite and install them
Overall Winner – Viessmann
The Viessmann Vitodens 050-W is a fantastic example of a modern condensing combi boiler, perfectly showcasing Viessmann’s signature top-of-the-range design and efficiency.
For a detailed breakdown of why the 050 is a great choice of boiler, watch our video review by clicking below…