Children do not spend enough time together say experts
But according to psychologists, far from bounding back to school this September, many children will slink back - taking a new social problem with them.
Dr Aric Sigman, who carried out research for Powergen, said children find it very difficult to settle back to school because they spend too much time alone in the holidays.
In interviews with 1,000 children, 50% said they had spent most of their summer holiday playing alone and on computers.
Only 13% of the children said they had spent most of their time playing with other children.
Dr Sigman said three out of four children had trouble socialising - a problem he calls September attitude disorder.
"Children are spending long periods of time alone during their summer holidays, and this, coupled with their increased use of the television, internet and computer games is making our children more selfish," he said.
"They are not learning how their behaviour affects real people - only virtual or TV characters - and so their negotiation and sharing skills really suffer."
He says children are so used to being their own boss in the summer that they find it hard to get on with both teachers and class-mates when they go back to school.
"This prevents them from developing impulse control and so there is an inevitable clash of cultures when they return to the classroom where they are required to conform, defer their gratification, and consider other people," he said.
Powergen says it commissioned the study because staff were surprised by an increase in electricity and telecoms bills over recent summers.
It says a key factor was the time children were spending watching TV or playing on the computer.