Boiler reviews: Reliability

We survey thousands of Which? members about problems they've had with their home appliances, to find out which brands are the most reliable. Here we reveal our results by showing you the most reliable boiler brands. To find out more about the features and performance of individual boilers, see our individual boiler reviews.

Boiler reliability

In our survey we found that problems with boilers are common - 49% of owners with boilers bought since 2006 have experienced faults with their gas or oil condensing boilers. Not all faults require a boiler repair, but three in 10 members have had a visit from the boiler engineer.

A leaky boiler or a frozen condensate pipe, are the most frequent problems, has affected 7% and 6% of people respectively. See our boilers FAQs page for advice on fixing a frozen boiler condensate pipe.

The most reliable gas boiler brands

Our reliability table below reveals the reliability of the gas boiler brands owned by more than 90% of the Which? members in our survey who own a gas boiler. All the major brands of gas condensing boilers are covered, including Baxi, Glow-worm, Potterton, Vaillant and Worcester Bosch.

One gas boiler manufacturer has good brand reliability. The brand reliability of several manufacturers is average and four manufacturers have below average brand reliability. 

To find out which they are, Which? members can log in to unlock the table below. Not already a member? Discover the benefits of taking a one month trial for instant access for £1.

Gas boilers Which? reliability index
AlphaSubscriber only contentSubscriber only content
BaxiSubscriber only contentSubscriber only content
British GasSubscriber only contentSubscriber only content
Glow WormSubscriber only contentSubscriber only content
IdealSubscriber only contentSubscriber only content
MainSubscriber only contentSubscriber only content
PottertonSubscriber only contentSubscriber only content
VaillantSubscriber only contentSubscriber only content
ViessmannSubscriber only contentSubscriber only content
VokeraSubscriber only contentSubscriber only content
WorcesterSubscriber only contentSubscriber only content

Table notes:
The average reliability score is 75%, based on 4,145 responses from people who bought a condensing gas boiler in the last six years.
Respondents for each brand are: Baxi (267); British Gas (177); Glow-worm (326); Ideal (195); Main (45); Potterton (172); Vaillant (848); Veissmann (131); Worcester (1,847); Vokera (55).

The most reliable oil boiler brands

Our survey revealed brand reliability for two major oil boiler brands, Worcester and Grant, which are the choice of two-thirds of Which? members with oil boilers. Other brands are owned by too few members for us to report statistically robust results.

Oil boilers Which? reliability index
GrantSubscriber only contentSubscriber only content
WorcesterSubscriber only contentSubscriber only content

Table notes:
The average reliability score is 70%, based on 272 responses from people who had bought a condensing oil boiler in the last six years.
The responses for each brand we have enough responses to report on are: Grant (127); Worcester (145).

Our research

In June 2014 we surveyed 10,119 Which? Connect online panel members about the problems that they had experienced with their main gas or oil central heating boiler. The reliability score is based on whether people who own boilers up to six years old have ever had to have their main boiler repaired since they bought or acquired it

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