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Which? reveals the best boiler brands for 2021

From Vaillant, Baxi, Glow Worm to Ideal boilers - find out what customers think of 17 top boiler brands, and which are the most reliable

Which? reveals the best boiler brands for 2021

Which? annual research on gas and oil boilers shows the best and worst boiler brands, according to boiler owners and heating engineers.

Two brands were reliable enough, and received high enough praise from both customers and heating engineers, to get our Best Buy recommendation.

Read on to find out what our surveys uncovered about the best and worst boiler brands.


To find out how each brand performs, go straight to our best and worst boiler brands guide


Best new boilers

family in kitchen eating a dining table

In May-June 2021 we asked 8,001 members of the public, who bought a boiler in the past six years, to tell us how satisfied they are with their boiler, and if they would recommend it to a friend.

We also asked 153 Which? Trusted Trader heating engineers for their views on each brand. Combining this with the customer and reliability score gives a brand it’s overall score.

This gives a holistic picture of just how good the UK boiler manufacturer’s are – and it’s the biggest brands aren’t necessarily the best.

Below are all the brands identified in this year’s survey, and a typical price range across their models. Find out how they scored by following the links.

The price doesn’t include installation costs, such as labour and fittings. Factors such as what price your installer can get a model for may increase or decrease the price you pay, but the typically price on our boiler reviews should give you a good sense of typical costs.

Brand Price range
Alpha £560 – £2,330
Ariston £1,220 – £2,950
ATAG £1,390 – £2,095
Baxi £550 – £1,210
Biasi £540 – £720
Ferroli £580 – £670
Glow Worm £560 – £1,660
Grant (oil boilers) £1,480 – £3,150
Heatline £390
Ideal £510 – £2,560
Intergas £630 – £1,420
Main £520 – £690
Potterton £700 – £800
Vaillant £940 – £1,770
Viessmann £780 – £2,480
Vokera £470 – £910
Worcester Bosch (gas and oil boilers) £780 – £2,740
Price range is the highest and lowest price based on all boiler models on which.co.uk as of September 2021. For latest prices contact the manufacturer.

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Most and least reliable boilers

Getting a reliable boiler brand is vital. It will give you piece of mind and save you money in the long run, as you are not having to fork out on expensive repairs. Boiler owners in our survey said they pay, on average, £200 a time for a boiler repair.

To find out how reliable each boiler manufacturer is, we ask owners that have purchased their boiler new in the past six years to tell us whether their boiler has broken down and, if so, how often.

As you can see in the graph below, after six years the worst boiler brand is nearly twice as likely to have developed a fault compared to the most reliable Best Buy brand.

Read our Best Buy boiler reviews to discover the most reliable brand.

graph showing the percentage of fault free boilers versus the age of the boilers

An annual service will also keep your boiler reliable as it can be – read our guide to getting the best boiler service


What heating engineers say about boiler manufacturers

engineer inspecting boiler

We asked Which? Trusted Trader heating engineers what they thought about each brand, rating a brand on five factors. This generates a boiler brands engineer score.

Some engineers are incentivised by manufacturers to install their boilers, we filter out responses from these engineers. This ensures that the views and ratings from engineers is independent and unbiased. Here is what they had to say about:

The best overall boiler brand

  • ‘Incredibly reliable. Rarely have a problem with them. Great customer service and spare parts are reasonably priced.’
  • ‘Excellent product with the best service and back up.’
  • ‘Newer versions have improved layout and accessibility, making repairs and servicing easier.’

The worst overall boiler brand

  • ‘Dreadful products. Bespoke parts means it’s usually difficult to get spare parts.’
  • ‘Very poor, cheaply made, would not recommend.’
  • ‘Poor quality boilers and components with bad after sales support.’

The boiler brand they gave five-stars across the board

  • ‘Wonderfully easy to install and service. A top quality boiler, easily in the top three for quality and reliability.’
  • ‘Excellent build quality and very reliable.’
  • ‘Excellent product range with excellent manufacturers guarantee.’

Which? boiler reviews

Couple on laptop

We don’t just rely on one opinion or source of information to score boiler brands.

  1. We ask engineers to rate boilers on five factors – build quality, availability of spare parts, how easy the boilers are to service and repair, and if they would recommend the brand -this makes up a brands engineer score.
  2. We ask customers with the boilers in their homes if they are satisfied with the brand, and if they would recommend them – this makes up a brand’s customer score
  3. We also ask customers if their boiler has developed a fault, and how many – this generates a brand’s reliability score.

We turn all of this data into easy-to-understand star ratings and an overall Which? test score, so you can see at a glance the brands we recommend and the ones you should avoid. We pair this with detailed specification information from every boiler within each brand’s range.

Need a new boiler? Our guide on how to buy the best boiler will help you find the right type, size and brand for your home

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