Buying Guide, Price Comparison & Reviews of Viessmann Vitodens 100-W Combi Boiler

The boiler has been one of the most revolutionary inventions by John Mills in the year 1870. Since then, they have just gained more and more popularity with time due to their effectiveness and functionality. The reason that boilers are highly effective in keeping us warm throughout the winter season and are very efficient as well, makes them the best heating system available in the market.

Boilers radiate heat through the inside surface of the house with the help of pre-installed pipelines. They also provide hot water from taps in bathrooms for bathing and washing purposes. They can be attached to several radiators around the house to provide for an excellent central heating system.

Viessmann is a German brand that has always excelled in the manufacture of boiler systems in the UK market. They are known to be one of the most efficient boiler brands and are highly durable as well.

NameOur RatingAvailabilityPriceCustomer Rating
  Viessmann Vitodens 100-W Combi Boiler  9.6/10  YES  £1,097.67 to £1,159.05 including VAT and excluding installation.  4.5 out of 5 stars and 712 reviews.

About Viessmann Vitodens 100-W Combi Boiler:

Combi boilers are the units that provide both heating and hot water for your house. Viessmann vitodens 100-w combi boilers are one of the most efficient sets of boilers which also require very little space in your house for installation. They do not need any additional hot-water cylinders or cold-water tanks to function. They are a gas-fired and wall-mounted set of combi boilers. They also come with a standard warranty of 10 years when installed by a Viessmann trained installer otherwise, it is for 5 years.

Prices for different models of Viessmann vitodens 100-w combi boiler range:

Model NameMax Flow RateDimensionsOutputWarrantyPrice
  VIESSMANN VITODENS 100-W COMBI 26KW  10.6M  H-700MM, W-400MM, D-350MM  26KW  5 years  £ 1114.88
  VIESSMANN VITODENS 100-W COMBI 30KW  12.3M  H-700MM, W-400MM, D-350MM  30KW  5 years  £ 1097.67
  VIESSMANN VITODENS 100-W COMBI 35KW  14M  H-700MM W-400MM, D-350MM  35KW    5 years  £ 1159.05


  • Highly efficient and helps save money on gas bills.
  • Perfect for installation near busy rooms due to very low operating sound.
  • Environment-friendly with low CO2 emission.
  • Very easy and simple to operate boiler controls.
  • Can be operated from anywhere around the house with a mobile app.
  • Peace of mind with a 10-year warranty upgration.
  •  Enhanced performance with a stainless-steel heat exchanger.
  • Tested and endorsed by Which? In 2017.
  • Takes very little space.
  • Quick and efficient services available at your doorstep.
  • 5-year labor and parts warranty.
  • No need for any additional hot or cold-water storage in the house.


  • Small unit boilers are not that effective.
  • Not suited for very large commercial buildings or properties.

Unique features:

  • Rated-A by SEDBUK for efficiency.
  • Simple Backlit LCD touchscreen controls.
  • Inox-radical stainless-steel heat exchanger.
  • Low CO2 emissions.
  • Pre-heat function is available.
  • Combined Pressure Release Valve (PRV) & condensate connection
  • Compatible with the Tado° thermostat and app.
  • 5-year parts and labour warranty.

Technical specifications:

Model Units:26kw30kw35kw
Gas supply pressure (Natural Gas)202020
Gas supply pressure (LPG)373737
DHW performance @ 35˚C temp. rise10.6 l/min12.3 l/min14.3 l/min
Lift weight36 kg38 kg38 kg
Total weight (including packaging)38 kg40 kg40 kg
Electricity supply230v 50 HZ230v 50 HZ230v 50 HZ
Max power consumption119 W135 W154 W
DHW outlet & inlet15 mm15 mm15 mm
CH flow & return22 mm22 mm22 mm

Buyer’s guide for Viessmann vitodens 100-w combi boiler:

As a customer one gets very confused when looking for the right boiler system. The reason behind is that the market is so full of variants that are so different from each other depending upon different wants and needs of the different customer group. For that reason, you need to first know what you exactly want from a boiler depending upon several factors. These factors are:

  1. Size of the house- Viessmann vitodens 100-w combi boilers come in a variety of ranges depending upon different heating units for different sizes of the house. For smaller houses with very little hot water needs one can choose the 26kw boiler, for medium-sized houses the 30kw boiler is the best, and for larger houses with multiple bathrooms the 35kw unit boiler is the best option.
  • Hot-water demand- Viessmann vitodens 100-w combi boilers are a great option if you are looking for a boiler that can meet the high demand for hot water in the house. They are the best boiler system for houses with multiple bathrooms to provide water from several taps simultaneously.
  • Efficiency- If you are interested in a highly efficient boiler, Viessmann vitodens 100-w combi boiler is your best choice. They are rated A by SEDBUK with 89.5%. It also comes with an inox-radical heat exchanger with a very high-efficiency rating of 98%.

Facts You Didn’t Know About Viessmann:

  • The Viessmann Group was founded in the year 1917.
  • The Viessmann Group is one of the leading international manufacturers of heating, cooling, and climate control technology.
  • It maintains a staff of around 12,300 employees and generates a turnover of 2.6 billion Euros annually.
  • Its headquarters is in Allendorf (Eder).


What Do The Experts Have To Say?

  • Trustpilot rating: Great (from 9 verified user reviews) ★ ★ ★ ★ ★
  • Which? rating: 86% ★ ★ ★ ★ ★
  • Eco Experts rating: ★ ★ ★ ★ ★

Our boiler experts gave Viessmann an overall rating of 4 out of 5.

That’s better than Ideal (3 out of 5), on a par with Vaillant (4 out of 5), and not quite up there with Grant and Worcester Bosch (5 out of 5).


Customer reviews:

  • Name of the customer- Sandra
  • Rating– 4 out of 5 stars
  • Feedback– Satisfied

advised against this “due to the presence of electrical installations”. As a result, the boiler was installed in my kitchen, resulting in a kitchen wall unit destroyed, broken tiles, exposed pipework, exposed plasterwork, other damage, and reduction in sink draining board area. Opinions given by other tradesmen suggest that garage installation was not a problem, especially if a site survey had been undertaken before commencement of work.

  • Name of the customer- Anonymous
  • Rating– 2 out of 5 stars
  • Feedback– Installation took too long

Detail- The installation of the boiler took 7 weeks from start to finish after many missed appointments. The installer also failed to install correctly causing water to flood through the light sockets in the bathroom ceiling. It was a very traumatising experience. Also, the manual for the thermostat is very unclear and I still have not managed to set it correctly. Very very upset and unhappy about the service.

  • Name of the customer- Steve Place
  • Rating– 5 out of 5 stars
  • Feedback– Fully satisfied

Detail- Envirowarm Services LTD (based in Hull) recommended and installed a quality Viessmann boiler in my house 10 years ago (saving me a lot of money over the British Gas quote for a lesser boiler) and have serviced it ever since and carried out the replacement of what I consider to be serviceable items on it recently. We have found the quality of our Viessmann boiler to be excellent over the last 10 years and Envirowarm Services LTD to be reliable, with friendly, trustworthy staff that are highly qualified and experienced. Prices for boiler installation, servicing, and repair have always been very reasonable.



When is the right time to replace my heating system?

Knowing when to arrange heating system replacement isn’t always easy, but several signs suggest it’s time to make a change.

The occasional heating system breakdown may not warrant a replacement, but if your system needs to be repaired frequently, it could be time to get a new solution. Also, if your heating system is old and you find it difficult and expensive to source replacement parts for it, it’s worth considering making the switch to something new.

It may also make sense to get a replacement if your current heating system isn’t working as well as it used to, or if it no longer meets the needs of your household. Besides, you may benefit from getting a new solution if your current system is proving inefficient and therefore costly to run.

Which heating system is best for my home?

Deciding its time for heating replacement is one thing, but how do you know which system is right for your home? With so many solutions available, it pays to do your research – and you may wish to take expert advice to help you find a system that matches your priorities and the specific heating and hot water needs of your household.

How do heat pumps work?

These pumps use the natural heat source, whether this is the ground or air surrounding your property, and increase it to provide a source of warmth for your home. They use the same principle that allows your fridge to cool food and drink but in reverse.

The warmth from the air or ground is either pumped or blown over a heat exchange surface. This heat, although much cooler than the temperature inside your home, is warm enough to cause a refrigerant liquid to evaporate and turn into gas. 

The pressure of this gas is then increased using a compressor, which causes its temperature to rise – and the heat created is transferred into your central heating and hot water system.    

How efficient are heat pumps?

All heat pumps need some electricity to run, but because they are highly effective at extracting renewable heat from the environment, their energy output is considerably greater than their electricity input. 

This means that both air source and ground source heat pumps can help you to lower your home’s energy bills and carbon emissions.

Most heat pumps can also be connected to a solar thermal system to provide the power required to operate, making them even more environmentally friendly and efficient.

Is a gas safety check different from a boiler service?

A gas safety check is different from a service, but the two things can be done together. A gas safety check includes all the tests and checks required to make sure your boiler is safe to use. This means ensuring that the appliance is physically stable, the gas is burning as it should and any chimneys or flues are working correctly. It’s important to be aware that this check doesn’t help to maintain the reliability and performance of your appliance.


Real-World Use Case:

by Gordon Hitch

I have just had a boiler repair done by an engineer and when he left, I noticed a slight leak I contacted customer service and they said they couldn’t come and sort it until I had requested my service contractor (that’s a whole other nightmare). I was then told by the customer service agent that their engineers do not make mistakes and that the leak must have happened some other way after he had left. to me, that suggests they are blaming us for tampering with the boiler. After speaking with Julie at Viessmann today I have changed my score slightly I still think a boiler retailing at £825 should not have had repairs done to it totaling £842 and that’s with £200 credit after only 4.5 years. I will get this boiler removed as soon as I can as I have no doubt it will keep costing me in years to come. My last boiler lasted 18 years with no flushes and no issues at service.

Thanks again to Julie for all your help as without it this review would have been very different


Choosing the right heating system in a market where there so many options available can be too overwhelming. Boilers are known to be the best central heating system due to their high efficiency and low maintenance. They are best for radiating heat in the house and also for providing hot water for bathing and washing. So, do get a boiler for your family this winter season!

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