While some 4.31 million meters were not operating in smart mode as of June 2023, that figure decreased to 3.98 million by the end of last year, according to data from the Department for Energy Security and Net Zero (DESNZ).

It previously said 2.7 million were not working properly as of June 2023, but revised the figure citing data errors from a minority of suppliers.

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Smart meters are considered an important tool to help energy customers manage their use of gas and electricity.

They work by sending gas and electricity use data in real time to energy suppliers and show customers how much their energy use is costing them.

When they are not connected properly customers instead receive estimated bills, meaning they could be overcharged. Customers are encouraged to send in meter readings to ensure their bills are accurate.

Not-so-smart mode

Trade association Energy UK, which represents suppliers, said "technical problems can prevent some meters from operating in smart mode" and suppliers are obliged to replace them when this happens.

A spokesperson said: "Customers should always contact their supplier if they are experiencing issues - there can be a range of potential fixes so these are best addressed on a case-by-case basis.

"It is of course important that figures correctly represent the current situation and we continue to work with suppliers and other partners in the programme to further improve the customer experience for smart households."

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'Vast majority are operating as intended', non-profit says

Smart Energy GB, a non-profit organisation, said it understood the "frustration" of people whose meters are not working properly.

It said there are now nearly 35 million smart meters in Great Britain and "the vast majority are operating as intended".

It said 88.6% were operating in smart mode at the end of last year, up from 87.3% the previous year.

"If your smart meter is not sending automatic readings to your energy supplier, please be reassured that it will still be recording your energy use correctly," a spokesperson said.

"We would recommend that you send your supplier meter readings to make sure you receive accurate, rather than estimated, bills until all of the features of your smart meter have been restored."

Minister calls for energy regulator to hold suppliers to account

Lord Callanan, Minister for Energy Efficiency and Green Finance, has written to Ofgem, the energy regulator, calling on them to take action to hold underperforming energy suppliers to account.

A spokesperson for Ofgem said it had asked suppliers to provide more detail on how they plan to tackle connectivity issues.