Switching of energy suppliers has surged to a six-year high as householders increasingly shop around for better deals on gas and electricity.
Customers swapped their energy providers 7.7 million times last year, according to the regulator Ofgem, a rise of 1.7 million, almost 30%, on 2015.
It comes as consumers face a spate of price rises in recent months, hitting the pockets of many who are already struggling.
Npower, EDF and Scottish Power are among those to have ramped up bills, with many blaming rising wholesale costs.
On Thursday Co-operative Energy announced it would increase the cost of its standard variable tariff by an average of 5%, a change that will affect around 96,000 customers when it comes in from April 1.
Earlier this month Ofgem set a temporary pre-payment price cap to protect more than four million households least able to benefit from competition following a two-year investigation of the energy market by the Competition and Markets Authority.
Ofgem advised consumers they can make substantial savings by shopping around for energy deals, warning that standard variable tariffs are typically more expensive than fixed deals.
Despite rising switching rates, around two thirds of customers still remain on standard variable tariffs.
Of those who did switch last year, 47% were to small or medium suppliers as they continued to attract growing numbers of customers.
Ofgem's chief executive Dermot Nolan said: "This welcome increase in switching should serve as a warning to supply companies.
"If they fail to keep prices under control or do not provide a good service, they risk being punished as customers vote with their feet.
"While today's figures show good progress, the market is not as competitive as we would like.
"That is why we have put a temporary price cap in place to protect people on pre-payment meters who have the least access to competitive deals and why we are pursuing a raft of reforms which will make this market fairer, smarter and more competitive for consumers."
"Big savings of around £230 are available and switching has never been easier, so we would urge everyone to shop around for a better deal, especially if their supplier announces a price rise."
Lawrence Slade, chief executive of the industry's trade association, Energy UK, welcomed the high numbers of people swapping their power providers.
He said: "With ever increasing numbers of consumers switching, it's clear competition is working for more and more households.
"The industry is committed to ensuring the market works for everyone and is taking action to engage with loyal customers."
Despite the rise in switching, complaints about energy transfers fell last year, from 4,755 in 2015 to 3,066 in 2016.
Lewis Shand Smith, chief ombudsman at Ombudsman Services, said: "Switching is an important tool for consumers to get the best energy deal they can, but switching can be tricky and time-consuming, and this is putting a lot of people off.
"Last year we received 3,066 complaints about switching, down by 36% from 2015. This indicates that companies are getting better at managing transfers and any complaints related to them, which is good news for consumers.
"If something does go wrong, the company you're switching to should be able to resolve the problem.
"If your complaint hasn't been resolved in eight weeks, Ombudsman Services: Energy will be able to review your case for free."