The number of energy customers looking for cheaper deals soared at the end of last year, with around one million people switching energy suppliers over November and December.
In contrast, around 208,000 people switched in September and 3m switched over the entire year, according to research from data company Electralink.
230,000 of those switching in the last two months of 2013 chose smaller independent suppliers outside of the big six.
"There has been a sharp increase in the number of customers switching and those shopping around for a deal which suits their individual circumstances," said Angela Knight, chief executive of industry body Energy UK.
"And competition is alive and well, with people choosing new entrants to the market and smaller suppliers rather than just sticking with established companies."
A debate into energy prices and the cost of living rumbles on, with the suppliers blaming rising wholesale costs and green levies for ramping up bills.
The government has pledged to move some of the environmental charges away from energy bills and into general taxation. The big six have promised to pass these savings onto consumers.