More than four million households in the UK that remain on a standard energy tariff have been urged to send in meter readings to avoid paying higher prices starting October 1. This follows a recently announced government goal that all homes in England, Scotland and Wales get a smart meter by the end of 2030. Under current rules, suppliers can’t require consumers to  get a smart meter, however, if their current traditional meter is approaching the end of its life, they may have to by default.

After October 1, the average household in England, Scotland, and Wales will see the energy price cap increase by 4%–just as cooler temperatures will prompt many to turn on their central heating.

The energy bill for the average household paying by direct debit for gas and electricity will increase to £1,723, up £5 a month or £60 a year if this level continued over 12 months.

Great Britain’s Office of Gas and Electricity Markets (Ofgem) said the increase reflected higher wholesale gas prices as a result of the ongoing conflict in the Middle East, with volatile global markets remaining the dominant driver of price changes.

Households without smart meters that didn’t send readings to their supplier by the end of September will now be charged higher rates for energy used before October 1, according to energy comparison site Uswitch.

Homes on a standard tariff with average usage are expected to spend £145 on energy in October, compared with £109 in September.

The increase of a third is down to a combination of increased usage due to cooler temperatures and higher unit rates under the latest price cap.

“Submitting a meter reading, if you don’t have a smart meter, before or on Thursday October 1 will ensure the energy used is charged at the correct rates and not estimated by a supplier,” said Ben Gallizzi, a spokesperson for Uswitch.com. “That same deadline applies for the 15 million households on standard tariffs wanting to beat the hike entirely by locking in a lower-rate fixed deal before energy costs rocket for winter.”

Ofgem changes the price cap for households every three months, mainly based on the cost of energy on wholesale markets.

The energy price cap was introduced by the UK government in January 2019 and sets a maximum price that energy suppliers can charge consumers in England, Scotland, and Wales for each kilowatt hour (kWh) of energy they use.

It does not limit total bills because householders still pay for the amount of energy they consume.