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Best combi boilers: the 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 crucual 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.

If you're unsure whether a combi is the best option for you, read our guide is a combi boiler the right boiler for you?

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 thecharts in our customer and engineers survey over the past few years. Its combi boilers are reliable and loved by those wh oown 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.

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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