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Best combi boiler brands

By Matthew Knight

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A good combi boiler will deliver plenty of hot water for your showers, baths and sinks, and will keep your radiators piping hot throughout the coldest of winters. 

What makes a good combi boiler?

To get the best combi boiler, it's crucial to go for a reliable brand that won't break down, and getting one that's the right size and fit for your home. 

An unreliable combi boiler will fail early and is likely to result in regular costly repairs. On average, it costs almost £200 for a boiler repair - so it pays to invest in one that will last. 

An oversized combi boiler will lead to you spending more on your heating and hot water than you need to, and an undersized one will deliver a disappointing flow of hot water to your taps and radiators.

Is a combi boiler right for you?

The first question to ask is whether a combi boiler is the right choice for your home. 

Combi boiler

Combi boilers don't require a hot water cylinder or cold water feed tank, so they're great if space is an issue. They heat hot water on demand, so they're very efficient and minimise waste. But heating hot water on demand does mean that they're best suited to homes with only one bathroom, or where you typically only want hot water for one tap or shower at a time.

All modern boilers, including combi, heat-only/regular and system, are condensing boilers.

The top three combi boiler brands

We would only recommend buying a combi boiler from one of the three best combi boiler brands. 

Every year we survey more than 10,000 boiler owners so that we can tell you which boiler brands are the most reliable, and which ones leave their customers delighted. 

The least reliable boiler brands are more than twice as likely to break down in the first six years of life compared to the most reliable.

We ask expert heating engineers which brands they think are the best, too. In our comprehensive boiler reviews, our Which? Trusted Traders rate each brand for build quality, how easy the boilers are to repair, the availability of parts and spares, and ultimately how likely they are to recommend it.

Best combi boiler brand overall

Reviewed -

This brands boilers have topped the charts in our customer and engineers survey over the past few years. Its combi boilers are reliable and loved by those who own them and the engineers who fit and service them.

Most reliable combi boiler brand

Reviewed -

This brand of boilers has a peerless reliability record. It's also loved by its customers and heating engineers think its build quality is top notch.

Engineers' favourite

Reviewed -

This brand is completely adored by expert heating engineers. They rave about its build quality and award it 5 stars on every measure in our Which? Trusted Trader heating experts survey.

Which brands make combi boilers?

Combi boiler brands
Brand Summary



Alpha boilers has been gobbling up market share from its competitors over the last few years. Its range of combi boilers is called E-tec, Intec or Evoke, and they're priced between £520 and £2,500.

Read our Alpha combi boiler reviews to find out what expert heating engineers, and its own customers, make of the brand. 



Baxi is one of the biggest combi boiler manufacturers in the UK. Its range of EcoBlue, Duo-tec, Megaflow and Platinum combi boilers come in sizes to suit almost any size and type of home, and they range in price between £650 and £1,200.

But are Baxi boilers reliable? And what do expert heating engineers make of them? Head over to our Baxi combi boiler reviews to find out if it's worth investing in a Baxi or if other boiler brands are a better bet. 



Glow-Worm have several ranges of combi boilers including Energy, Essential, Betacom, Easicom and Ultimate. Its combi boilers range in price between £615 and £1,250.

Read our full reviews of Glow-Worm combi boilers to find out how long they last, what its customers make of them and expert ratings from heating engineers. 




Dutch manufacturer Intergas is the new kid on the block in the British boiler scene. It claims to have fewer moving parts in its combi boilers than its rivals, and a super reliable heat exchanger. It has two combi ranges, Rapid and Compact, which are priced between £630 and £1,040, potentially making them an attractive budget option.

But is Intergas all that reliable? And what do heating engineers and its own customers make of them? Read our Intergas combi boiler reviews to find out. 



Potterton has a number of combi boilers to pick from that suit all size homes. Its combi boiler ranges are called Promax, Titanium, Promax Ultra, Assure and Gold, and are priced between £675 and £1,350.

Read our Potterton combi boiler reviews to find out if they'll outlast the competition and what expert heating engineers make of them.



German manufacturer Vaillant is a large combi boiler manufacturer whose ecoFIT and ecoTEC range of combi boilers cost between £1,100 and £1,400, which puts them at the more premium end of the market.

Are Vaillant boilers worth the cost? Read our independent Vaillant combi boiler reviews to find out if they'll last longer than the competition and what customers and expert heating engineers make of the brand.



Viessmann is a German boiler brand making waves in the UK boiler scene. Its Vitodens combi boilers cost between £900 and £1300 and come in a variety of sizes to suit any home. 

Read our Viessmann combi boiler reviews to find out how long they last compared to competitors, and whether it has the respect of its customers and expert heating engineers. 

Worcester Bosch

Worcester Bosch

German manufacturer Worcester Bosch is one of the biggest combi boiler manufacturers in the UK. Its combi Greenstar range starts at £875 and goes up to over £2,000, depending on the size and hot water flow you need for your home.

Read our Worcester Bosch combi boiler reviews to find out how it compares to its competitors for reliability, customer satisfaction and according to the views of expert heating engineers. 



Best combi boiler for your home

Once you've picked the brand of boiler you want from the three above, the next thing you'll need to decide is what size boiler is right for your home. 

The size of the combi boiler refers to its heat output, which is measured in kW (kilowatts). Put simply, this tells you how much water the boiler can heat up and send whizzing around the pipes in your home. A larger home with more radiators and pipes to navigate will require a larger combi boiler. 

The simplest way to estimate the size of boiler you might need is to count the number of radiators you have. Use the table below for a rough guide. 

What size boiler do I need?
How many radiators are in your home Boiler size in kW
<10 <27kW
10-15 28-34 kW
>15 >34kW

Table notes
1 This table provides a rough guide. A fully trained heating engineer will be able to more accurately size your boiler after a full heat loss survey of your home. Never buy a boiler before a trained heating engineer conducts a full heat loss survey of your property.

Best combi boiler installer

Proper installation is key to the ongoing health and efficiency of your combi boiler. 

Poor installation can lead to early failure, as well as money wasted on repairs and through having a heating system that isn't as efficient as it should be. 

Read our guide on how to get the best boiler installation before you buy a new combi boiler and cross reference the quotes you receive with our guide to boiler prices: how much does a new boiler cost?

We'd recommend using a Which? Trusted Trader, too. They have all been vetted by a trading standards officer, and the satisfaction of their customers is regularly monitored to ensure they are the best of the best in their trade. 


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