Martin Lewis has warned households that an energy bill hike of up to 60% is coming - and it will mean an extra £623 to £723 per home.
Speaking on ITV's Good Morning Britain this morning, the MoneySavingExpert founder said a price cap which is keeping energy bills artificially low is set to rise today.
Lewis said: "At 11 I am expecting to hear the price cap is going to be increased on April 1 by between 50 and 60%, that's the range. We have a pretty good idea, because the assessment period that the price cap is based on ended on the last day of January."
The price cap limits variable rate energy deals.
These are the deals people are on if they come off a fixed-rate deal and don't switch to another fixed rate but stay with their same provider.
The price cap also limits how much you pay if your energy company went out of busines s and you have been switched to a new deal with another provider.
It is set twice a year by the energy regulator, Ofgem.
Many energy firms have been unable to take the extra strain of rising gas prices they cannot pass on due to the cap, and have been forced to stop trading .
Around 70-75% of homes in the UK are on deals subject to the price cap, but it does not apply to Northern Ireland.
Lewis added: "That price cap, the one we've had since October, has protected us from the huge, enormous, unprecedented spike in energy prices that has been going on. We have been paying less than the market would have us pay, by a substantial amount."
The average consumer would pay no more than £1,277 a year under the current price cap.
But Lewis said this will almost definitely rise to between £1,900 and £2,000 on April 1.
"That's an enormous £600 rise," he added.
Why are energy bills going up?
They are rising for several reasons.
Much of the increase reflects the soaring cost of gas, not electricity.
Reasons behind this rise include supply and demand, as there was a very cold winter in Europe last year.
British homes are heavily reliant on gas, making the problem worse.
Most homes (86.3%) have gas central heating, the Office for National Statistics has said.
What to do if your energy firm stops trading
If your energy firm collapses, the advice from Ofgem is to sit tight and wait until your new supplier contacts you.
You should wait until you know which firm you've been moved to before you decide to look into switching elsewhere .
In the meantime, take a meter reading for when your new supplier contacts you so it can correctly bill you.
It is important to check prices as soon as you know which deal you've been moved to, as you may not necessarily be transferred over to the cheapest supplier.
You won't be charged exit fees for switching away from your new energy provider.
