Martin Lewis is urging households to take a meter reading on Thursday this week (March 31) before a huge energy price hike come into force.
Ofgem is increasing its price cap on April 1. For those on a default tariff who pay by direct debit, the price cap is going up by almost £700 in a huge hit on household bills.
But MoneySavingExpert Martin has explained that if you take a meter reading on March 31, you can tell your energy provider exactly how much gas and electricity you used before the price cap increase.
"That way you draw a line in the sand that says to your energy firm, I've only used this amount at the cheaper rate," he said on his ITV Martin Lewis Money Show Live series finale earlier this month.
"Don't start charging me more on the higher rate and estimating I use some of it afterwards."
The energy price cap for those on default tariffs who pay by direct debit is rising by £693 from £1,277 to £1,971 from April 1.
Prepayment customers will see a bigger jump, with their price cap going up by £708, from £1,309 to £2,017.
Are you worried about paying your energy bills? Let us know: mirror.money.saving@mirror.co.uk
The energy price cap isn’t an absolute cap on bills, as its name suggests - instead, it sets a limit on the rates a supplier can charge for each unit of gas and electricity you use.
It is important to send regular meter readings, otherwise your energy supplier will estimate your usage and you could end up being overcharged.
A digital meter will show five numbers in black or white, and might be followed by one or more red numbers.
To send a meter reading, you'll need to send the first five numbers shown from left to right (you can ignore any red numbers) to your energy supplier.
You should be able to do this over the phone, online or through an app.
In more energy bill news, Martin Lewis has apologised after giving advice about "stockpiling" gas and electricity before the price cap hike.
The MoneySavingExpert founder previously said customers who topped up old-style prepayment meters (not smart meters) before the price cap rise on April 1 would be charged at the cheaper rate.
But in an update this week, Martin said some of the energy companies that MSE had previously spoken to had backtracked on their earlier confirmation.
Martin said his website team had received written proof of the prepayment meter trick from all major firms except Scottish Power.
They now say it might work with all providers except for Scottish Power and E.on - and only for electricity customers, not gas.
In the MoneySavingExpert email last week, he said: "I wanted to write this personally, as unfortunately information we were given by energy firms and the regulator no longer looks watertight."
