Annual energy bills could reach £4,347 for an average household after the government announced the two-year price freeze will now run for just six months.
New chancellor Jeremy Hunt said the universal energy price guarantee will finish next April, with a review being launched on how to then support bills after this period.
The government said its changed approach after April will “cost the taxpayer significantly less than planned” and will target those most in need of support.
It also confirmed that the energy bill relief scheme for businesses, which will cap corporate energy bills, is also set to end in April.
Following Mr Hunt’s announcement as part of the mini-budget U-turns, energy market analysts Cornwall Insight said a typical household could face bills of £4,347 a year.
Liz Truss’s government had launched the support scheme at the start of last month to limit the unit cost of energy so that a typical household will pay a maximum of £2,500 annually.
Energy regulator Ofgem previously had raised the cap to £3,549 from October, necessitating a government intervention that came in the form of the energy price guarantee.