Regulator Ofgem said there were 3.8 million switches in the first six months of the year.
This was the second six months in a row that the switching total broke three million, and was nearly one million higher than the first half of 2015.
The data follow a major report into competition in the energy market.
According to the Competition and Markets Authority's (CMA's) two-year investigation, two-thirds of UK households were paying "over the odds" for their energy compared with those who have switched to a different tariff.
Ofgem said that customers could save more than £300 by ditching expensive standard variable tariffs for the cheapest deal, often a fixed-term tariff.
The average standard variable tariff of the larger energy suppliers as of 28 July was £1,066. The cheapest tariff available on that date - a one year fixed tariff - was £758, a saving of £308.
"Great deals are there for the taking. There are very competitive offers and many more suppliers to choose from, and that's why more consumers are switching," said Rachel Fletcher, of Ofgem.
To encourage more switching, Ofgem is planning to trial "more effective prompts" on customers' bills to encourage them to compare different tariffs. However, Ofgem said it would not be capping standard variable energy tariffs.
The regulator's response to the CMA report, and the investigation itself, was criticised by some as not being bold enough.
Separately, the Energy Networks Association has launched a new service in England, Scotland and Wales allowing people to contact their network in the case of a power cut by calling 105 or visiting a dedicated website.

Michelle O'Neill hosted a departmental breakfast at the Balmoral Show on Thursday morning.
In attendance was the Chinese consul general Madam Wang Shuying.
Chinese inspectors visited Northern Ireland pork plants in April as part of a process to approve local pork for export.
Ms O'Neill said she was also hoping to agree access to Chinese markets for beef and chicken.
US consul general Greg Burton was also at the event.
Northern Ireland is hoping to sell beef into the United States.
Ms O'Neill said she was also working with Irish agriculture minister Simon Coveney to resolve labelling issues that have hit Northern Ireland lamb sales to meat plants in the Republic of Ireland.
She told guests that the quality of Northern Ireland food was "something that carries our reputation around the world."
She said it was "safe, traceable and sustainably produced" and she would seek to use that reputation to open doors.
It is the second day of the Balmoral Show, the biggest showcase for Northern Ireland's farming and food industries.
A rising number of energy customers have switched gas and electricity deals amid widespread calls to benefit from savings that are available.
[NEXT_CONCEPT]
The agriculture minister is to return to China next month as attempts to access markets there continue.