More than 2.8 million households changed their electricity or gas supplier in the first seven months of 2007, says the energy regulator Ofgem.
Switching has helped to force bills down, Ofgem says
The regulator hailed this as a further success for the policy of deregulating the domestic energy market.
Approximately half of all households in the UK have now switched their gas or electricity supplier since 1998.
Ofgem says the people with most to gain are those who have never switched before or are on pre-payment meters.
"Now is a good time for all customers to check whether they are getting a good deal for their energy," said Ofgem chief executive Alistair Buchanan.
"This is particularly true for pre-payment meter customers, who can reap savings on average of £100 if they have never switched supplier," he added.
Ofgem added that in some parts of the country pre-payment customers can save as much as £170 a year, compared with average savings of between £60 and £86 a year for ordinary customers depending on whether they pay by direct debit or not.
Energy tariffs have been coming down this year after peaking in 2006 when domestic energy bills rose rapidly as a result of higher oil and gas prices.
At one stage the average household in the UK was paying well over £1,000 a year for their heating, lighting and power.
Urged on by the government, the regulator and consumer bodies, slightly more households have switched supplier this year than in the first seven months of 2006, when 2.68 million households made a similar move.
It means, according to Ofgem estimates, that nearly half of UK homes have changed an energy supplier at least once since the market was opened up.