Worcester Bosch vs Vaillant Boilers – Which is Best? Re February 22, 2023

Worcester Bosch vs Vaillant Boilers – Which is Best?

Boiler in kitchen

When it comes down to buying a new boiler, after all the research has been done, the choice usually comes down to the big boys – Worcester Bosch or Vaillant boilers. Think of them as Cristiano Ronaldo vs Lionel Messi of the heating world. Both boiler brands have an excellent reputation, and both build excellent boilers, but which is the best boiler?

In this article, we will give you a bit of background on both companies and compare top-end boilers such as the Worcester Bosch Greenstar 8000 Life 35kw combi gas boiler and the Vaillant ecoTEC plus 835 Combi Gas Boiler. We will also be comparing other like-for-like boilers representing the latest technology in the gas combi boiler, system boiler and regular boiler market. In terms of what defines the best boiler, we would say it comes down to a few key factors – price, reliability, energy efficiency, and aftercare.

Want to know what the best combi boilersystem boilers and regular boilers are on the market? Well, don’t worry, we have other blogs that cover this.

Time to compare

If you’re looking for a new or replacement boiler but you’re unsure what model or brand to choose from, we also have a Boiler Comparison tool, that allows you to compare up to three boiler models and brands at one time, to help you decide on the perfect boiler for your home.

Let the fight commence!

Worcester history

Worcester was formed in 1962 in Worcester, where it takes its name. It started off as a small engineering works before growing into the biggest boiler manufacturer in the U.K. The company was acquired by Robert Bosch Holdings in 1992 to join the German-based Bosch group forming the Worcester Bosch Group. 

Worcester Bosch currently holds the Royal Warrant to supply heating to the Royal Family and has won the Which? Best Buy award for their range of boilers for the last ten years. This prestigious award is judged on reliability, build quality, recommendation, and customer score.

For a full timeline of Worcester Bosch’s history click here.

Vaillant History

Vaillant was formed way back in 1874 by Johann Vaillant in Remscheid, Germany. Johann Vaillant, the tenth child in his family, founded his own workshop as a copper beater and pump maker.

Many inventions have been credited to Vaillant over the years including modern-day central heating in 1924. Previously each room was heated individually by stoves or fireplaces until Vaillant introduced the central heating boiler that could heat multiple radiators simultaneously – revolutionising home heating.

The Vaillant boiler range has been given a Which? Best Buy award and they have also been awarded a Quiet Mark Accreditation, from the Noise Abatement Society for their quiet running boilers.

For a full timeline of the Vaillant company history click here.

Comparison tables

Below we will look at comparable 35kW boilers from both Worcester and Vaillant and compare key stats to see if we can separate these two boiler powerhouses.

Combi boilers

Boiler makeWorcester BoschVaillant
Boiler modelGreenstar 8000 Life 35kW Combi Gas BoilerecoTEC plus 835 Combi Gas Boiler
Boiler typeCombiCombi
Fuel typeGasGas
Suitable forLarger homes with up to 20 radiators and 2 bathroomsLarger homes with between 15 and 20 radiators and up to 2 bathrooms
Is CondensingCondensingCondensing
Efficiency Rating94%89.3%
Band RatingA RatingB Rated
LPG CompatibleYesNo
Standard Warranty5 Years*5 Years*
kW Output35kW35kW
MountingWall Mountable Wall Mountable
Flow Rate14.3 l/min14.3 l/min
Typical price*£2,729.00 (inc. VAT)£2,819.00 (inc. VAT)
ErP ratingA Heat | A WaterA Heat | A Water
Smart thermostat compatibleYesYes
Shock Arrestor standardNoNo 

As you can see from the table above, there is very little between these two boilers in terms of performance. They come with the same water flow rate of 14.3 litres per minute and have an ErP rating of A for both heating and water.

Where they differ is that the Vaillant ecoTEC comes in £90 more expensive than the Worcester 8000 Life and the Vaillant has a lower energy efficiency rating. Most modern boilers have an energy efficiency rating of over 90%, meaning they will save you money on your energy bills and they are better for the environment.

This is probably a great time to explain exactly what your boiler package comes with when purchasing from WarmZilla. Firstly, this price includes the costs for installation and labour charges. In addition to this you get a flue kit, a free Honeywell RF wireless room thermostat, a system cleanse to ensure that your heating system is clear from any debris or sludge build-up before your new boiler is installed, a chemical initiator for extra protection, a magnetic filter for ongoing protection and removal of your old boiler and parts, Yes, I know, it sounds too good to be true. 

On top of all this, you get an extended guarantee, in this case, an additional 3 years on the Vaillant, taking you up to 8 years guarantee and a total of 10 years with the Worcester Bosch. What more could you ask for? 

Let’s have a look at two more combi boilers you can buy with WarmZilla

Boiler makeWorcester BoschVaillant
Boiler modelGreenstar 4000 25kWecoTEC Pro 24kW
Boiler typeCombiCombi
Fuel typeGasGas
Suitable forHomes with up to 15 radiators and 1-2 bathroomsHomes with up to 15 radiators and a bathroom
Is CondensingCondensingCondensing
Efficiency Rating94%94%
Band RatingA-RatedA-Rated
LPG CompatibleYesYes
Standard Warranty10 Years2 Years*
kW Output25kW24kW
MountingWall MountableWall Mountable
Flow Rate12 l/min9.6 l/min
Typical price*£1,969.00 (inc. VAT)£1,979.00 (inc. VAT)
ErP ratingA Heat | A WaterA Heat | A Water
Smart thermostat compatible YesYes
Shock Arrestor standardNoNo

A combi boiler is a very popular choice when it comes to buying a new or replacement boiler for your home. It can be installed neatly into your kitchen cupboard, due to its compact size, which makes it the perfect choice for homes with limited space. It combines both a water heater and the central heating element within the unit itself. They are also lightweight so they are easy to install.

Again, when comparing both of these boilers, there is very little difference in performance. Both combi boilers offer the same efficiency rating and the same ErP rating, however, for a cheaper price, the Worcester Bosch Greenstar 4000kW offers a higher flow rate and a 10-year warranty. With that said, when you purchase a Vaillant ecoTEC Pro with WarmZilla, you will get an extra 8 years warranty on top of the standard warranty offered, if the Vaillant is more up your street. 

Now that we’ve compared the most popular combi boilers, let’s compare some system boilers. 

System boilers

Boiler makeWorcester Bosch Vaillant 
Boiler modelGreenstar 4000 24kW ecoTEC Plus 624 (24kW)
Boiler typeSystemSystem
Fuel typeGasGas
Suitable for Homes with up to 15 radiators and 1-2 bathroomsHomes with up to 15 radiators and 1-2 bathrooms
Is CondensingNon-CondensingNon-Condensing
Efficiency Rating94%94%
Band RatingA-RatedA-Rated
LPG CompatibleYesYes
Standard Warranty10 Years5 Years*
kW Output24kW24kW
MountingWall Mountable Wall Mountable 
Flow RateN/AN/A
Typical price*£2,319.00 (inc. VAT)£2,399.00 (inc. VAT)
ErP ratingA Heat A Heat 
Smart thermostat compatibleYesYes
Shock Arrestor standardNoNo

Both the Worcester Bosch Greenstar 4000 24kW system boiler and the Vaillant ecoTEC Plus 626 (24kW) system boiler are similar in performance, with the same efficiency rating, the same ErP rating and the same kW output. The Worcester Bosch comes in at £80 cheaper than the Vaillant although this is a newly introduced model from Worcester Bosch.

Both system boilers are compact and lightweight for easy installation. On the other hand, it is important to remember that when purchasing a new or replacement system boiler, you will need to ensure that you have the room in your home for an additional hot water cylinder, which is usually installed in an airing cupboard. Although system boilers take up more room in your home, they are ideal for those that require hot water ‘on-tap’ (excuse the pun 😉).

Regular boilers

Boiler makeWorcester BoschVaillant
Boiler modelGreenstar Ri 18kW ecoTEC plus 418 (18kW)
Boiler typeRegular Regular
Fuel typeGasGas
Suitable forHomes with up to 15 radiators and a bathroomHomes with up to 15 radiators and a bathroom
Is CondensingCondensingCondensing
Efficiency Rating92%94%
Band RatingA RatingA Rated
LPG CompatibleYesNo
Standard Warranty8 Years*5 Years*
kW Output18kW18kW
MountingWall Mountable Wall Mountable
Flow RateN/AN/A
Typical price*£2,129.00 (inc. VAT)£2,159.00 (inc. VAT)
ErP ratingA Heat A Heat
Smart thermostat compatibleYesYes
Shock Arrestor standardNoNo 

From looking at the comparison table, there are pros and cons about both regular boilers. Some could argue that the Vaillant is a better boiler with an efficiency rating of 94%, however, for us, Worcester Bosch pushes into first place with a standard warranty of 8 years, which can be extended to 10 years when your buy a new or replacement Worcester Bosch boiler with WarmZilla a well as being slightly cheaper. 

Regular boilers are installed alongside an additional hot water cylinder, that is typically installed in an airing cupboard or similar size space. They also need a cold water tank and a feed. These are usually installed in the attic of your home. The cold water is supplied from the mains and then fed into the cold water tank, this is then fed down to the boiler, where the water is then heated. Any water that is not used is then stored in the hot water tank until needed.

Both boiler brands offer reliable and robust boilers that will not let you down, however, when it comes to comparison, round 1 goes to Worcester Bosch. 

Reliability - Vaillant boiler reviews vs Worcester Bosch boiler reviews

Worcester have won the Which? Best Buy award for their range of boilers for a staggering ten consecutive years. This prestigious award is judged on reliability, build quality, recommendation and customer score.

Consumer review site Which? Has the following to say on Worcester Bosch:

“Reliability is the single most important consideration when buying a new boiler and Worcester Bosch has it in spades”

“We’ve been running boiler reliability surveys for 10 years now, and Worcester Bosch has impressed us every year”.

Worcester Bosch boilers come out on top from industry side reviews with a Which? brand score of 92% compared to Vaillant boilers brand score of 78%. 

However, Vaillant has higher ratings than Worcester Bosch for ease of service and repair, which means that they could be easier to maintain from a heating engineer perspective.

Heating engineers often cite the stainless steel heat exchanger of the Vaillant as a clear advantage over the aluminium heat exchanger in the Worcester boiler. If you get an issue with the heat exchanger in your boiler it’s a serious issue and often leads to the replacement of the boiler.

Worcester Bosch has a 4.7 rating on Trustpilot compared to Vaillant’s score of 4.6 out of 5 on Trustpilot, so from the customer point of view, Worcester Bosch boilers come out just ahead of Vaillant.

In terms of reliability, Worcester Bosch has the vote of the industry review sites and the public, whereas Vaillant takes the heating engineer vote. Again, a close-run battle in which the Worcester brand just comes out ahead.


Both the Worcester Bosch Greenstar 8000 Life and the Vaillant ecoTEC plus 835 Combi Gas Boilers offer a standard 5-year warranty on their boilers. 

Worcester offers an extended warranty of ten years when the boiler is fitted with a Worcester System Filter by an accredited Worcester installer.

Vaillant offers a 5-year extension on the warranty if registered by a Vaillant Advanced Installer. Both brands give you ten years cover when fitted by one of their accredited installers. 

To maintain the warranty on your boiler you will need to have an annual service carried out to ensure any claim you make against your warranty won’t be rejected.

Worcester enjoys an excellent reputation for their response time to customers calling on their warranty with an issue, often getting an engineer out the next day. They are the most reactive boiler brand on the market in terms of customer care.

Vaillant are no slouches either, with great response times as indicated by their high rating on Trustpilot.

Again, both companies offer excellent service but Worcester just edge it with another win in the final round.


So in answer to the question ‘Is Vaillant or Worcester the better boiler?’, the answer is very close but Worcester Bosch just shades it. Despite Worcester just pipping Vaillant to the post in each of the key factors of price, reliability, energy-efficiency, and aftercare you can see that there is very little between the two brands.

Both are very reasonably priced, both offer excellent aftercare and customer service and both have won numerous awards on their boiler range.

We would recommend Worcester as the number one choice boiler manufacturer as they are slightly cheaper, more energy-efficient, offer better customer service, and have a slightly better review score from the public on Trustpilot.

Industry awards can sometimes be biased depending on who has relationships with who, but consumers aren’t afraid to give their honest opinion and if they have a boiler that lets them down they will write about it. Vaillant and Worcester being 4.6 and 4.7 respectively on Trustpilot show you that in terms of reliability there isn’t much to choose between the brands but Worcester just shade it.

Whichever of the two brands you go for you’ll be getting a reliable boiler from two companies with a proud history of innovation and customer focussed development.

*Prices are taken from the WarmZilla survey. Please note that these prices are based on a 3 bedroom home with one bathroom. Prices may vary depending on your demands. 

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