Nine million households must submit their energy meter readings by January 1 to avoid overpaying on their bills, the results warn.
Comparison website Uswitch says Britons risk overpaying a combined £66m if accurate meter readings are not provided.
This is because their suppliers will bill them based on estimates, which are usually higher.
In November, Ofgem said the cap price will rise to £1,738 per year for a typical home using both electricity and gas, from January 1, 2025.
Households on standard variable tariffs and without a smart meter risk having some of their energy consumption estimated and potentially being charged new, higher tariffs unless they submit a meter reading before January 1.
The difference between a week’s energy consumption at January rates compared to December is £6.67 per household on average, totaling £66 million across Britain.
Meter readings: nine million households must submit them by January 1
About 14 per cent of Britons who needed to submit meter readings said they were unsure how to do so, while 12 per cent said they didn’t know where their meter was, Uswitch said.
According to the research, households with typical energy consumption will spend £165 on energy in January due to higher usage and tariffs, compared to £135 in December.
Elsie Melville, energy expert at Uswitch, said: “Customers who do not have a smart meter should try to submit their readings on or before Wednesday 1 January, so their supplier has an up-to-date and accurate view of their account.”
‘If you leave it later, then some of your December energy consumption could end up being estimated and therefore charged at the higher January rates.
“Now is also an ideal time to consider switching to a new energy tariff, as there are currently a variety of fixed offers available that are cheaper than the January price peak.
‘By opting for a fixed deal, you are locking in those rates for the entire time, meaning households could have price certainty and avoid the ups and downs of the price cap.
“Make sure you are happy with the length of the contract and any early departure charges.”
EOn told its customers: “Customers on a standard variable tariff, such as Next Flex, and who do not have a smart meter should submit a meter reading by January 5 to avoid the supplier having to estimate usage.”
Industry analyst Cornwall Insight has predicted the top price will rise 1 per cent in April to £1,762.
This would mean a third consecutive increase for households on default rates, following a 1 percent increase in January and a 10 percent increase in October.
Regulator Ofgem has urged households to take advantage of the growing options on the market and shop for the best deal to help keep their bills down.
A fixed energy deal, unlike an SVT, could help some households save money on their bills and help lock in cheaper rates than January’s peak price.
However, some fixed tariffs are more expensive than simply staying on an energy tariff capped by Ofgem’s price cap.
Among other methods, draft-proofing your home, reducing your boiler’s flow rate and installing thermostatic valves on your radiators could help keep your bills under control amid rising bills.
> How to save money on energy: read our essential guide