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Vaillant Boiler Review

Vaillant Boiler Review is something you would be “Google-ing” or “Bing-ing” online for in 2018, especially because it came up as a Best Buy Boiler for 2017 alongside Worcester Bosch and Viessmann.  If you are in the market for a new boiler because your old one is not working how it used to, or has recently suffered from a bad breakdown, then a Vaillant boiler is definitely one of the top boiler choices.  You as a consumer have to do your research before buying any product, especially when it’s an expensive, long-term purchase like a boiler installation.  And our job, as a boiler installation company and an online resource for boiler and central heating related information, is to give you unbiased, technical reviews and comparisons.

Obviously, a major purchase such as a boiler should not be made lightly or rushed into.  Which is why, even if you may or may not be freezing right now, we appreciate you clicking through to our site and reading this article.

Vaillant are definitely one of the most popular and renowned boiler manufacturers in this country, and even in mainland Europe right behind Viessmann.  When people argue about boilers these days in 2018, it is mostly about Viessmann vs Worcester-Bosch, sure – but normally a Vaillant Boiler Review will get thrown into the mix for good measure too.  And with good reason.  Vaillant have been making quality products for many years now.  So, chances are you will be buying a high efficiency and reliable boiler when you’re buying a Vaillant.

One of the major talking points about Vaillant boilers, that you may or may not know is the fact that they are actually Quiet Mark accredited for their incredibly silent operation.

Undoubtedly one of the best selling and most popular from the Vaillant boiler range is their EcoTec Plus line.  Known for delivering superb performance and on-demand hot water in a very compact and neat package.  In this Vaillant Boiler Review we will look at the Vaillant EcoTec Plus 35kW 835 combi boiler.

vaillant boiler review

  • Vaillant ecoTEC Plus 835 Combination Boiler Natural Gas
  • Warranty: 5 Years
  • Width x Height x Depth (mm) – 440 x 720 x 372
  • Weight: 38 kg
  • Output: 35 Kilowatts
  • ErP Space Heating Efficiency A
  • ErP Water Heating Efficiency A
  • Noise Level (Decibels) 45
  • Flow Rate (L/min) 14.3
  • Fuel Natural Gas
  • Mounting Wall Mounted

Vaillant Boiler Review – The Pros

Flow Rate And Output

As the Vaillant EcoTec Plus 835 has a central heating output of 35kW, it is able to heat a big 4 bedroom house with around 10 to 13 radiators, very comfortably.  Therefore, if you have a smaller sized home, you are probably better off opting for a smaller model.  In terms of hot water, the 835 produces 35kW at around 14.3 litres per minute straight into your taps.  This boiler is ideal if your home has two bathrooms and you will be able to run a bath and two showers with it.  A word of warning though, it would be prudent to test the water pressure coming into your home’s system beforehand, because you won’t get the optimal experience from your new boiler if you don’t have enough water pressure coming from your mains water supply.

Compact Size And Other Key Features

If you have serious concerns about the impact your new boiler will have on available space in your home, the EcoTec Plus is ideal for you.  As there is no need for a separate storage tank or hot water cylinder, this boiler has a very streamlined and compact design as it has been pointed out in many Vaillant Boiler Reviews.  In fact, it is possible to fit it inside a kitchen cupboard.  On top of that, it’s a well-designed, handsome looking boiler, so it won’t be an eyesore.

The Warranty

While it is fair to say we hope you don’t have a problem with your Vaillant boiler, but it is as well to have a little foresight into what your options are if something goes wrong.  Vaillant give a standard 5 year warranty, as well as fully dedicated engineers who know their way around a Vaillant machine like no other.  Now, a standard warranty of 5 years is not that amazing compared to other manufacturers and approved installers who can give warranties of 7-10 years and above.

Technical Specification

One of the biggest concerns we know most people have nowadays when it comes to investing in boilers is that they will be as high on the energy efficiency as possible.  We all want to get as much for as less as possible, don’t we?  The Vaillant actually has a reasonably high ErP score of 89.3% energy efficiency, so it’s maybe not as high as let’s say a Viessmann, but it’s definitely up there with other condensing boilers in its price range.

Vaillant Boiler Review – The Cons

About That Efficiency Rating

Almost all of the major “UK Based” boiler manufacturers are actually headquartered in Germany or Netherlands or other countries in Europe.  Now, because both Viessmann and Vaillant are number 1 and 2 in the German market, we thought it’d be a fair comparison to compare their boilers.  Also, both are A-rated, high efficiency condensing boilers.  Vaillant’s impressive 89.3% efficiency still sees the Vaillant come up short compared to a Viessmann Vitodens 200-W which goes up to a whopping 98% efficiency (used with smart controls and weather compensation) on some models.

Now, at Boilerhut, while doing this Vaillant Boiler Review, we are aware and can do the math and realise that the difference between the similarly priced Vaillant EcoTEC Plus (89.3%) and Viessmann Vitodens 200-W (97% and above)  is a whopping 8%.  Is 8% really such an issue then?  The short answer is yes.  As a famous saying goes, every drop fills the pot.  That 8% extra fuel saved goes a long way over the long-term in saving you tons of money on your energy bills.  What’s even more incredible is that the Viessmann 200-W is only about £100 more expensive.  Seasons will come and go, and especially with the stainless steel heat exchanger inside the Viessmann, carrying 10 years warranty, your boiler will keep running at the highest efficiency for a long, long time.  Because when it comes down to it and you are looking for something with reliability in the long-term, every extra % is very important.


Again, there is not much in the way of a difference when it comes to the size of both a Viessmann and a Vaillant.  With the Viessmann coming in only slightly more compact.  But if you are working with small storage and installation spaces, all those extra millimetres will make a difference.  A lot of Vaillant Boiler Reviewonline won’t touch on this point.


The Vaillant boiler is more expensive than Viessmann boilers of similar specification.  Which on the surface may mistakenly make Vaillant seem like a premium product, but surprisingly and unfortunately it’s not.  Viessmann are able to offer a more attractive price point because they manufacture their Inox-Radial Stainless Steel Heat Exchanger and condensate+pressure release valve and other components in-house.  Whereas Vaillant source a lot of those components from third parties.  Also, when you take into consideration the fact that Viessmann 050-W and 100-W have a smaller, more compact design, have the same or higher efficiency than the Vaillant, and are cheaper by almost £200 to £400 (for the 050-W), these little points add together to make them a lot more substantial.

Vaillant Boiler Review – Our Verdict

Although Vaillant are undoubtedly good at what they do, and we would not judge anyone for choosing to have a Vaillant boiler installed in their home.  But it’s important for you, as a consumer, to do your due research online and elsewhere, weighing up all the options as we’ve discussed, and choose the best boiler for your needs.  Now, we are Viessmann Approved Installers, and it may appear on the surface that we are biased towards Viessmann.  But that bias is not based off of just conjecture or opinion.  They are based on cold, hard facts.  Let’s take a look at why:

combi boiler viessmann 100-w

Viessmann Boilers

  • Have an Inox-Radial Stainless Steel Heat Exchanger. (Patented technology and manufactured in-house)
  • Have the Condensate Pump and Pressure Release Valve combined into one unit. (Again, manufactured in-house)
  • One of the few boilers in the world with built-in shock arresters which makes it very quiet at only 45 decibels.
  • Components mentioned above are manufactured in-house, which means Viessmann can offer a more attractive price point.
  • A-Rated, above 90% efficiency, condensing boiler. (Close to 98% efficiency on a 200-W with Weather Compensation)
  • High end boilers at the cutting edge of technology at an amazing price.
  • Compact design, easier to site.
  • 10 Years Warranty if installed by a Viessmann Approved Installer like Boilerhut.

Based on the facts above, we have no hesitation in recommending a Viessmann boiler over a Vaillant.  However, we have no issues installing a Vaillant or a Worcester-Bosch or a Baxi or Ideal boiler.  Our installation teams spread all across the UK are Gas Safe Registered and with years of experience behind them, will gladly install the boiler of your choice.  Even if they prefer to install Viessmans because they are easier to install!

You can get an online estimate for a complete boiler installation on our website.  Simply enter your postcode in the box below and hit the green button to get your online boiler quote:

As we mentioned above, when you get the online estimate from us, it includes:

  • A brand new A-rated condensing boiler
  • Standard or Vertical Flue
  • Magnetic and Limescale/Hardwater Filters
  • Wireless Programmable Roomstat
  • Chemical Flush or Power Flush
  • Pipework to Complete Installation
  • Registration of Warranties (7-10 Years)
  • Commissioning, building regs, hand over, induction on boiler controls & best usage
2 replies
  1. R. C. Clark
    R. C. Clark says:

    I have a Veissmann boiler fitted 4 years ago and have had nothing but trouble with it over those years. I would give it one star and say it is absolute crap. I shall be on the market for a new boiler later this year and it certainly will not be a Veissmann. My Wife needs 24 hour care so we have to have a reliable boiler as she feels the cold. As you can see by my moans my boiler has just broken down again.

    • Bryn Lloyd
      Bryn Lloyd says:

      Hi there,

      Thanks for getting in touch – we’re sorry to hear about your situation. If you’d like some assistance in choosing your next boiler, we’ll be happy to assist you. You can contact us via email on or call us directly on 029 2009 9898 to chat with one of our heating experts.

      Thanks again!

      Kind Regards,
      The Boilerhut Team


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