Millions of people will pay an extra £693 a year on their energy bills from April, regulator Ofgem has said.
A higher price limit means nearly 18 million households in England, Wales and Scotland will typically pay £1,971 a year for gas and electricity.
Another 4.5 million people on prepayment meters will see an even bigger increase of £708 a year.
Chancellor Rishi Sunak is expected to outline plans to ease the pressure on bills within an hour.
The Bank of England is also widely expected to raise interest rates on Thursday, which will make borrowing money more expensive for individuals, but is designed to keep a lid on soaring prices.
Soaring energy bills are the key factor in what the Resolution Foundation think-tank has described as a “cost of living catastrophe” facing people across the UK this year.
Jonathan Brearley, chief executive of Ofgem, said: “We know this rise will be extremely worrying for many people, especially those who are struggling to make ends meet, and we will ensure energy companies support their customers in any way they can.”
Food bills are also rising, and a increase in National Insurance will leave millions with a higher tax bill from April.