More than half of British households are set to see an increase in the cost of energy in April owing to higher price caps.
Regulator Ofgem sets maximum prices that can be charged for gas and electricity to those who have not switched and are on default tariffs.
The new cap could see these households typically pay an extra £117 a year.
The regulator is allowing suppliers to cover the higher costs they face on the wholesale market.
“We can assure these customers that they remain protected from being overcharged for their energy and that these increases are only due to actual rises in energy costs, rather than excess charges from supplier profiteering,” said Dermot Nolan, chief executive of Ofgem.
About 11 million households are on default, or standard variable tariffs, and are set to be affected. Such a household, which uses a typical amount of energy and pays the bill by direct debit, should now expect to pay £1,254 a year.
Consumer groups say they can shop around for a better deal.
Another four million people are on prepayment meters, so pay for their energy in advance. The price cap will rise on their tariffs too.