Which? made 432 calls to 36 energy suppliers to reveal how long customers were left waiting before speaking to a member of staff.
Each provider was called 12 times at different times of the day and on different days of the week to calculate the average call waiting time for customers.
Scottish Power was the worst provider and left customers waiting for an average of 21 minutes and 24 seconds before calls were answered – 20 minutes slower than the fastest company, So Energy, which answered calls in just 38 seconds.
On some occasions, it took more than 30 minutes for calls to be answered.
Last year, Scottish Power was the fastest of the Big Six – and was 23 minutes, 52 seconds faster than the slowest company, Spark Energy which left customers on hold for 27 minutes and 21 seconds on average.
Bulb Energy kept customers on hold for an average of 19 minutes and two seconds before calls were answered, and had the longest single call waiting time of 41 minutes and 48 seconds. In less time, a customer living in Harlow would be able to travel by train into London’s Liverpool Street station, next to Bulb’s HQ, to make a complaint in person.
The challenger company has enjoyed meteoric growth, gaining a million customers and five per cent share of the electricity market in under five years and was the fastest to answer its customers’ calls in our snapshot investigation two years ago, but it has not compared as well since.
Just over a fifth of suppliers included in our research – Avro Energy, Boost, Bulb Energy, Engie, Green Network Energy, Utilita, Utility Point and Scottish Power – kept customers waiting for more than 10 minutes on average.
More than half of the suppliers Which? investigated had an average call waiting time of more than five minutes, including four of the Big Six.
So Energy was the fastest company when it came to answering calls, on average customers were left on hold for just 38 seconds.
The four fastest firms to pick up after So Energy were Ampower, Ebico, Flow Energy and Together Energy – all answered calls in less than a minute.
EDF Energy was the best of the Big Six, answering calls in three minutes and two seconds on average.
Twelve of the companies Which? investigated also offered a live chat for customers to seek help. Spark Energy, which was bought by Ovo last year, was the fastest to respond, taking just 30 seconds on average.
Three other firms – Outfox the Market, Scottish Power and Utility Point – also responded to live chat in under a minute, on average.
At the other end of the scale, British Gas was the slowest company to respond to live chat queries – with an average wait of seven minutes and 14 seconds in our investigation.
Customers would get a quicker response on the phone, where British Gas answered calls in four minutes and 19 seconds on average.
Which? found two companies – Bulb and Utilita – whose live chat platform was unavailable 11 out of the 12 times researchers attempted to test it.
The huge variations in waiting times highlight a lack of consistency on customer service within the industry and the need for companies to up their game and deliver the service consumers expect.
When choosing an energy provider, Which? recommends customers consider all factors including value for money and customer service. In Which?’s 2019 satisfaction survey, Octopus Energy was rated as the best provider, achieving five-star ratings in all categories including phone customer service and value for money.
Natalie Hitchins, Which? Head of Home Products and Services, said:
“Energy customers should be able to expect good customer service from their supplier, so it is unacceptable that some people are facing waits of half an hour or more just to speak with an adviser.
“If you are tired of poor customer service and wasted time on the phone, then you should switch to a provider that can better meet your needs, and potentially save you hundreds of pounds.”