Nine million households need to submit energy meter readings by 1 January to avoid overpaying on their bills, findings warn.
Comparison website Uswitch says that Britons risk overpaying by a collective £66million if accurate meter readings are not submitted.
This is because their suppliers will bill them based on estimates, which are often higher.
In November, Ofgem said the price cap will increase to £1,738 per year for a typical household using both electricity and gas, from 1 January 2025.
Homes on standard variable tariffs and without a smart meter risk having some of their energy usage estimated and potentially being charged under new, higher rates, unless they submit a meter reading on or before 1 January.
The difference for a week’s worth of energy at January rates compared with December is £6.67 per home of average, totalling £66million across Britain.
Meter readings: Nine million households need to submit them by 1 January
Around 14 per cent of Britons needing to submit meter readings said they were unsure how to do so, while 12 per cent said they did not 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 rates, compared with £135 in December.
Elsie Melville, energy expert at Uswitch, said: ‘Customers who don’t have a smart meter should aim to submit their readings before or on Wednesday 1 January, so their supplier has an updated – and accurate – view of their account.
‘If you leave it any later than this, then some of your December energy usage could end up being estimated and therefore charged under the higher January rates.
‘Now is also an ideal time to look at switching to a new energy tariff, as there are a range of fixed deals currently available that are cheaper than the January price cap.
‘By opting for a fixed deal, you’re locking in those rates for the duration – which means households could have price certainty and avoid the ups and downs of the price cap.
‘Make sure you are happy with how long the contract lasts and any exit fees for leaving early.’
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 before 5 January to avoid the supplier having to estimate usage.’
Industry analyst Cornwall Insight has predicted that the price cap will rise by 1 per cent in April to £1,762.
This would spell a third consecutive increase for households on default tariffs, following the 1 per cent rise in January and 10 per cent increase in October.
Regulator Ofgem has urged households to take advantage of rising choice in the market and look for the best deal to help keep their bills down.
A fixed energy deal, as opposed to a SVT, could help some households save money on their bills and help lock in rates cheaper than the January price cap.
However, some fixed rates work out more expensive than simply staying on an energy tariff limited by the Ofgem price cap.
Among other methods, draught-proofing your home, reducing the flow rate on your boiler and fitting thermostatic radiator valves could all help keep your bills in check amid rising bills.
> How to save money on energy: read our essential guide