The Big Six energy companies are facing renewed criticism for poor levels of customer service.
A survey by the consumer group Which? of more than 8,900 people found three of the six had below average customer satisfaction ratings while the other three were only just above average.
For the sixth year running Npower had the lowest customer satisfaction rating with 41%, closely followed by Scottish Power with 44%, while SSE, with 52%, was just below the average of 53%.
Eon with 53%, British Gas with 54% and EDF with 55% were just above the average.
For the fifth year running, the best performers were smaller companies with OVO Energy on 82%, followed by Good Energy with 81% and Ecotricity with 77%.
Despite the poor satisfaction ratings, 87% said they were still supplied by one of the Big Six with just 10% having switched their provider over the past year.
Which? executive director Richard Lloyd said: "Once again the smaller energy suppliers are leading the way when it comes to customer satisfaction, leaving the Big Six providers in their wake.
"With energy customers facing big bills this winter, energy companies need to up their game and provide the service their customers deserve."
The industry body Energy UK said most customer complaints were about billing and the situation should improve as smart meters were rolled out.
"Companies work hard to get things right and, when things do go wrong, most complaints are dealt with by the end of the next working day," it said in a statement.