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1,220 reviews

Vaillant vs Viessmann - A Boiler Comparison

Both Vaillant and Viessmann repeatedly make the top 5 brands in both homeowner and engineer surveys, but which has the best Combi boiler for your home? We’ve compared Vaillant ecoTEC plus 835 vs Viessmann Vitodens 050-W on their key features to help you decide.

No to gas boilers

Vaillant and Viessmann offer a wide range of Combi, System and Regular boilers in a variety of outputs. This means that each is very likely to offer a suitable solution for your home. The flagship range from Viessmann is the Vitodens while the ecoTEC range comes out on top for Vaillant.

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Both are wall-mounted, Combi boilers which are powerful enough to provide heating and hot water for homes with 2-4 bedrooms and 2-4 inhabitants. While both are designed for natural gas they can be converted to LPG for off grid homes.

As Combi boilers these models do not require a hot water cylinder or feed tank as they take their water supply directly from the mains and heat it on demand.

Brand / Manufacturer Viessmann Vaillant
Boiler Model Vitodens 050-W 35kW Combi Gas Boiler ecoTEC plus 835 35kW Combi Gas Boiler
Other Outputs Available 29kW 25, 32 or 38kW
ErP Rating A (up to 93%) A (up to 93%)
NOx Emissions Class 5 (best) Class 5 (best)
Max flow rate litres/min 14.1 14.3
Hot Water Temperature Controls? Yes Yes
Concealed User Controls? No Yes
LPG Convertible? Yes Yes
Standard Warranty 3 years* with 10 year warranty on heat exchanger 5 years**
Dimensions 707 x 400 x 350mm 720 x 440 x 372mm

*Viessmann trained installers can offer extended warranties of up to 7 years.
**Vaillant Advance installers can offer extended warranties of 7 or 10 years.

Alternatively you can compare up to 4 different boiler models via our Comparison Tool.

Viessmann Vitodens 050-W 35kW Combi Gas Boiler

Key features:

  • High efficiency A rated modulating pump with a modulation range up to 1:4
  • Inox-Radial heat exchanger and cylinder burner made from stainless steel for high efficiency and reduced corrosion
  • Ideal for installation in smaller living areas due to compact dimensions with height of just 707mm and recessed fittings not requiring pipe cover
  • Easy frontal access to serviceable parts e.g. plate heat exchanger
  • Extensive range of accessories to make boiler suitable for either new build or replacement.
  • Electronic boiler control unit for thermostatic mode and weather compensated mode is already integrated alongside a frost stat. The outside temperature sensor is available as an accessory.

Vaillant ecoTEC plus 835 35kW Combi Gas Boiler

Key features:

  • User friendly backlit display with simple push button programming
  • Stainless-steel heat exchanger delivers high efficiency and reduced corrosion
  • Quiet operation with Quiet Mark accreditation which is awarded to manufacturers of the quietest products
  • Wide range of heating control options, from analogue timer to vSMART™ smartphone app
  • High performance delivering hot water within 5 seconds with no need for a hot water cylinder
  • Built in frost protection to keep the boiler working through coldest months.

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    Vaillant’s prices are generally a slightly higher than Viessmann. Based on our research the ecoTEC plus 35kW Combi is likely to cost approximately £1,250 – £1,350. The Viessmann Vitodens 050-W 35kW Combi boiler, however, tends to come in a little cheaper at £950 – £1,100. This means that in some cases choosing a Viessmann could save you between £300 – £400.

    However, these prices don’t include the cost of installation which will vary depending on which supplier you use. To get the best price for a new boiler installation, we highly recommend getting at least 3 quotes from different installers to give you the best chance of getting the perfect deal. You can get free quotes from trusted engineers near you by using our service.

    Brand Reputation

    Vaillant UK are part of the global hot water and heating corporation, the Vaillant Group, which operates sales companies in more than 20 countries while manufacturing and exporting on a worldwide basis. The Vaillant Group began in Germany as a family-owned company and has remained so for over 141 years.

    Viessmann UK are part of the Viessmann Group, an international manufacturer of heating and refrigeration systems for both domestic and industrial sites. Similarly to Vaillant, the brand was founded in Germany and has over 100 years of expertise in the heating industry.

    Repairs & Warranties

    Generally, standard warranties for both brands are between 2-5 years depending on which boiler model you choose. In the case of these particular boilers, Viessmann offer a 3 year warranty while Vaillant offer a slightly longer 5 year warranty. But it’s also worth noting that the Inox-Radial heat exchanger in the Viessmann is covered by a 10 year warranty which covers corrosion damage from leaks.

    However, if your boiler is installed by an engineer who has been trained / accredited by the brand they both offer extended warranties of up to 10 years.


    Viessmann and Vaillant both offer a wide range of controls including plug in analogue timers, programmable room thermostats, weather compensation and smart phone app based controls.

    However, in the case of these particular boilers, the Viessmann 050-W Combi is not smart phone compatible while the Vaillant ecoTEC plus can be controlled by the vSMART™ app based heating control. This means you can operate your boiler from an Android or Apple iOS smartphone. This self learning thermostat enables multiple users to control the heating from wherever they are in the world over an internet connection.

    App based control is available with other Viessmann boilers which are compatible with the Vitotronic control unit such as the Vitodens 100W or 200W.

    Which Boiler Comes Out on Top?

    In the case of these particular boilers, by choosing Vaillant you will get a slightly higher flow rate, a longer warranty, the option of a smart controls and an exceptionally quiet boiler with the Quiet Mark accreditation. However, these advantages are reflected in the fact that the Vaillant boiler has a higher price tag in most cases. The Viessmann is the less costly of the two and has more compact dimensions which may make it a more attractive option for homes with restricted space. And, despite the shorter warranty, the Viessmann heat exchanger is covered by a 10 year guarantee.

    In reality, whether you choose to invest in a Vaillant or a Viessmann boiler for your home, you’re making a wise choice. Both brands have great reputations amongst both homeowners and engineers for reliability and heating performance. In terms of energy efficiency the two brands deliver A rated products with almost identical efficiency levels which should keep your running costs and carbon emissions to a minimum. These brands have a long legacy of quality and innovation and their boilers are trusted by homeowners throughout the world.

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    REMEMBER: Installers will have their own experiences of each brand from past installations so it’s important to get advice from more than one engineer. You should check with the installer if they are incentivised to install a certain brand; if the answer is yes, keep in mind that you may not be getting impartial advice. However, if an installer has been specially trained to install a particular brand it could mean that you receive an extended manufacturer warranty.

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