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Baxi or Vaillant: Boiler Comparison & Reviews

Baxi vs Vaillant

Baxi and Vaillant are amongst the leading boiler manufacturers thanks to offering highly reliable and efficient boilers that are well reviewed by installers and homeowners.

When it comes to choosing a manufacturer for your next boiler, which is best: Baxi or Vaillant?

Baxi vs Vaillant

Baxi boilers

Baxi have built a strong brand in the UK as a reliable boiler manufacturer and their units are highly recommended by many boiler installers.

If you're looking for flexibility with the installation of your next boiler then a Baxi might be the best option thanks to their units having a twin flue system. A twin flue can stretch to a distance of 15 metres at a diameter of only 80mm which means they can be installed in an internal cupboard away from external walls.

Vaillant boilers

One of the most recognised manufacturers of quality boilers, Vaillant are well-reviewed by homeowners and installers alike.

A big benefit of installing a Vaillant boiler is how quiet they are during operation and is why they're the only boiler manufacturer to be awarded the Quiet Mark accreditation.

When it comes to comparing Vaillant with other boiler manufacturers, they often come out on top thanks to having a stainless steel heat exchanger. Aluminium is the most common material for heat exchangers, and while it is effective, stainless steel offers many more benefits:

  • Extends potential lifetime of the unit
  • Helps to increase efficiency
  • Much less likely to need repairing

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Baxi and Vaillant boiler ranges

Baxi and Vaillant both manufacture combi, regular and system boilers that run on natural gas – with Vaillant also offering some LPG models too.

Best combi boilers

A combi boiler is the perfect boiler for smaller properties with 1-2 bathrooms as they supply central heating and domestic hot water on demand, rather than storing hot water in a cylinder.

Both Baxi and Vaillant have a number of options when it comes to condensing combi boilers and comparing them can be a challenge.

Boiler Range CH output DHW output Efficiency
Baxi 825 21.2 kW 25 kW 93%
Baxi 830 21.2 kW 30 kW 93%
Baxi 836 26.4 kW 36 kW 93%
“>ecoTEC Plus 825 20.4 kW 25.4 kW 94%
ecoTEC Plus 832 25.7 kW 31.8 kW 94%
ecoTEC Plus 835 32.2 kW 35 kW 94%
ecoTEC Plus 838 30.1 kW 38.7 kW 94%

CH = central heating. DHW = domestic hot water.

A warranty period of up to 10 years is available when the boiler is installed by a Vaillant Advance Installer.

Best regular boilers

In terms of efficiency and warranty, the Baxi 800 Heat regular boilers are the best option between the ranges offered by Baxi and Vaillant.

Boiler range CH output Efficiency
Baxi 816 Heat 16 kW 93%
Baxi 825 Heat 25 kW 93%
Baxi 830 Heat 30 kW 93%
ecoTEC Plus 412 12.3 kW 94%
ecoTEC Plus 415 15.1 kW 94%
ecoTEC Plus 418 18.3 kW 94%
ecoTEC Plus 424 24.6 kW 94%
ecoTEC Plus 430 30.5 kW 94%
ecoTEC Plus 435 35.1 kW 94%

CH = central heating

Best system boilers

They way system boilers is somewhere between combi and regular units. While, like a combi, system boilers heat water from the mains, they store hot water in a cylinder for use at a later time rather than providing it instantly.

Baxi system boilers are available with lengthier warranties than Vaillant models (7-10 years compared to 5 years) but the ecoTEC Plus and ecoFIT Pure ranges from Vaillant are the slightly more efficient units.

Boiler range CH output Efficiency
Baxi 818 18 kW 93%
Baxi 824 24 kW 93%
ecoTEC Plus 612 12.2 kW 92%
ecoTEC Plus 615 15.4 kW 93%
ecoTEC Plus 618 18.5 kW 93%
ecoTEC Plus 624 24.4 kW 94%
ecoTEC Plus 630 30.4 kW 94%
ecoTEC Plus 637 37.6 kW 94%

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Baxi and Vaillant both have boilers endorsed by the Energy Saving Trust which will give you confidence they'll help save you money on your energy bills.

As we mentioned earlier, the stainless steel heat exchanger found in Vaillant boilers helps to increase their efficiency. Baxi boilers, on the other hand, use aluminium heat exchangers.


In terms of price, there isn't much difference between the boilers manufactured by Baxi and Vaillant. For all boiler types there's a range of models available with a price tag suit higher and lower budgets. On the whole, the most affordable units are manufactured by Baxi which could help with your decision making.

Baxi boiler costs Vaillant boiler costs
Combi £625 – £1,385 £875 – £1,600
Regular £662 – £1,095 £790 – £1,500
System £740 – £1,127 £590 – £1,500


A standard Baxi warranty will see that you're covered for 2 years but depending on the model you could be covered for as long as 10 years. No matter the length of the warranty, it will only cover the boiler itself and the integrated controls, not any additional accessories such as the thermostat.

Reading the terms of a warranty can be confusing but not when it comes to finding out more about Baxi boiler warranties as they've been approved by the Plain English Campaign, meaning that they're simple to get your head around.

Vaillant boilers come with a standard warranty of between 2-5 years, covering the parts and labour. For even more peace of mind, many of their units offer the opportunity to increase it to 7-10 years when installed by a Vaillant Advance installer. During a Vaillant warranty, boiler component failures are covered but in the event that the fault is caused by contaminated water, you will be charged for the repairs.

Which manufacturer comes out on top?

There are benefits to having either a Baxi or Vaillant boiler installed but some of their advantages are different, which could make one more suited to your home than the other.

Although it might only be a slight advantage in some cases, Vaillant offer the more efficient systems which could come as a result of the stainless steel heat exchanger.

If you're looking to relocate your boiler to a new location – especially if it's away from an external wall – then Baxi is likely to be your best bet. The twin flue system offers greater flexibility when it comes to installation, making it much more likely that the boiler can be installed in your desired location.

Ultimately though, for many, the decision to go with one boiler manufacturer over another comes down to budget. More often than not, Baxi boilers are the cheapest option but it’s worth remembering that the stainless steel heat exchanger found in Vaillant boilers increases efficiency for lower energy bills, extends the life of the boiler and greatly reduces the risk of a fault.

So, while a Baxi boiler might be the cheaper upfront option, in the long run you may well be better off with a Vaillant boiler.

More boiler brands

If you want to continue you your search for a boiler manufacturer, the list of leading boiler brands extends beyond Baxi and Vaillant:

  • Ideal Boilers
  • Viessmann
  • Worcester Bosch
  • On the whole, all of these brands are also well reviewed by consumers and installers – compare their units using our Boiler Comparison Tool.

    Once you find the right boiler manufacturer for you, you'll then need to find a heating engineer to carry out the installation. Hiring the right heating engineer is as important as installing the right boiler and that's where we can help.

    By completing our simple online form, you'll get free quotes from up to 3 boiler installers based in your local area. Getting more than a single quote will give you the greatest chance of finding the most competitive price.

    Need a new boiler?


    Get FREE quotes for a replacement boiler today.


Boiler Guide Team

About the author

Boiler Guide Team

Boiler Guide has been home to a host of heating experts who have helped millions of UK homeowners searching for advice and guidance. If you’ve got heating questions, we’ll have the answers.

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