Hertfordshire-based supplier Solarplicity was subject to more than 1,000 investigations into complaints last year, the Energy Ombudsman has revealed.

The supplier, which was today (21 January) shown to have come bottom of the annual Which? satisfaction survey, was subject to investigations into a total of 1,035 complaints in 2018.

Billing, according to the Ombudsman, was the main driver of complaints.

Avro Energy meanwhile, which is based in Leicestershire, was also revealed to have been subject to 177 investigations into complaints last year.

An Energy Ombudsman spokesperson told Utility Week: “In 2018 we accepted for investigation 1,035 complaints about Solarplicity and 177 complaints about Avro Energy.

“In both cases billing was the main driver of complaints.

“We are keen to work with both companies, as we are with all suppliers, to identify and help implement any improvements that can be made to customer service and complaint handling.”

Solarplicity, rated for the first time in the Which? survey, was the worst energy firm according to its customers, with an overall customer score of just 44 per cent.

It was the only provider to receive one-star ratings, including for customer service, both online and on the phone.

Additionally, three-quarters of its customers told Which? that it is poor or very poor at dealing with complaints.

Solarplicity also ranked second from bottom in the latest Citizens Advice customer service rating table. With a score of two stars out of five it came ahead of One Select, which ceased trading on 10 December, just two days after the table was published.

Speaking at Utility Week’s Energy Customer Conference in Birmingham last week, Michael Hill, complaint management expert at Resolver, told delegates that the service saw a number of complaints through its platforms before recent energy company failures hit the headlines.

“Complaints were becoming increasingly complex and more often than not about customer service,” he said.

Hill added: “A 10 per cent increase in customer satisfaction delivers a 13 per cent increase in loyalty.”

Solarplicity and Avro have been contacted for comment but Utility Week received no replies at the time of writing.