Martin Lewis has urged people to take their meter readings and submit them this week to avoid a last-minute scramble ahead of the energy price rise on 1 October.
The consumer champion said he wanted to avoid a repeat of what happened the day before April’s price hike when huge numbers of users crashed energy firms’ websites by sending gas and electricity readings on the same day.
Lewis said he wanted it to be "meter reading week" instead of "meter reading day" so the system would not clog up.
Prices will increase from Saturday under the government's energy price guarantee, which caps how much suppliers can charge per unit of energy used, meaning the typical household will pay £2,500 a year – almost double the average bill last year.
Some customers could pay much more depending on their energy usage.
Firms use meter readings to calculate the usage of direct debit customers over a period of time.
Submitting them will prevent energy companies from potentially overcharging by overestimating the amount of energy being used.
Lewis wrote in the latest Money Saving Expert newsletter: “The fact huge numbers did it on the same day [in March] meant energy firms' websites crashed and their phone lines went down.
"That led to huge frustration and time wasted for customers, and abuse for staff.”
He added: "I'm also concerned if that happens again, the many vulnerable people who need to call firms at the moment for support because they're struggling won't get through.
"So let's think of it as meter reading week."
Lewis repeated the plea during a BBC Radio 5 Live interview on Wednesday, adding the difference in the meter reading would be “tiny” if people took it a few days either side of 1 October.
He said some firms would allow customers to backdate the reading up to a fortnight, so they did not necessarily need to submit it on the day of the energy price rises.
He added households who use direct debit and ‘on receipt of bills’ should submit a reading.
The average household energy bill will rise from £1,971 to a frozen £2,500 on 1 October under the energy price guarantee announced by prime minister Liz Truss earlier this month.
This is an increase of 27% from the previous price cap, which limited the rate providers can charge customers on a standard variable tariff.
Overall, household bills will still be 96% higher than last year.
The price guarantee and the support scheme will save the typical household at least £1,400 for the next year compared with the October 2022 price cap.
Charities have warned that many households are already struggling financially and struggling with bills.
Industry regulator Ofgem had originally said average bills were due to rise by 80% to £3,549 on 1 October.