Energy bills could more than double to £4,200 a year by January, households have been warned.
The predicted surge is even more than feared after regulator Ofgem this week confirmed its price cap would be reviewed every three months, but also announced further, unexpected changes to the way it is calculated.
Investment bank Investec now thinks the price cap - currently £1,971 a year - will jump to £3,523 in October, then leap to £4,210 in January.
Martin Young, an analyst at Investec, said the January forecast is about £460 more than expected before this week’s changes.
Ofgem said it did “not recognise” the Investec figures, which were “a long way off any working estimates we are currently using”.
But it came as another estimate put January’s average energy bill at nearly £4,000 a year.
Energy consultancy Auxilione warned that the price cap, which sets bills for 24 million households, could be increased further than previously expected.
It said that between October and December the price cap is likely to be £3,488 per year for the average household.
But from January the price will soar by another £500, hitting £3,994, it estimated.
Predictions for January are still uncertain as there are more than three months left until the price is decided. October’s prediction is likely to be more accurate.
Meanwhile, an energy boss has urged the Government to give an extra £500 to every household to help with another looming surge in bills.
Greg Jackson, of Octopus Energy, said another package of measures was urgently needed.
He told the Mirror: “We can’t go into winter with the degree of anxiety that we now see about bills.
“For the incoming Prime Minister this should be the number one thing on their agenda.
“The baseline is, if the amount of help they announced previously was right, and the situation has got £500 worse by then, they need to look at for example another £500 of assistance.
“There are lots of ways of doing that and they need to look at ways that are targeted.”
Measures announced by former Chancellor Rishi Sunak in May included £400 for every household - regardless of income - from this October, with the money coming off energy bills.
Mr Jackson said there had been keen interest from customers who do not need the money to donate the funds to good causes instead.
