This includes 2.3 million domestic gas switches, and 3.1 million domestic electricity switches, as customers changed supplier, said OFGEM.
As of September 2016, around 56% of all switches went to Britain’s Big Six suppliers, around 20% to mid-tier suppliers and 23% to small suppliers.
In September, around 15% of electricity and gas customers switched suppliers, as switching rates (switches over a 12 month period) reached their highest level since February 2012.
There are big savings to be made by switching, with the cheapest deal currently on the market (£822 per year) around £250 less than the average large supplier standard variable tariff (£1,066 per year).
Rachel Fletcher, OFGEM senior partner, Consumers and Competition, said: “With the majority of switches taking place within 21 days, it’s never been easier or quicker to switch suppliers.
“However, while those who are active in the market are getting better deals, our data shows that 66% of all households remain on expensive standard variable tariffs.
“That’s why we are taking forward the Competition Authority reforms as part of programme to make the market more competitive, fairer and smarter.
“We want energy suppliers to reach out to people who have not switched and offer them a better deal – particularly disengaged loyal customers who are still on expensive standard variable tariffs – ahead of the delivery of the CMA reforms.
“Suppliers must do more to reach out to people who have not switched and offer them better deals so that competition drives down prices for everyone, including loyal customers. Otherwise public trust will not be restored in the energy market.
“There are big savings to be made from shopping around for a better deal and consumers can get helpful advice at www.goenergyshopping.co.uk “.