Customers of the energy supplier Ovo were left shocked and dismayed when they received bills of up to £49,000 because of data errors that led to vastly overinflated energy projections for some households. Julie Lines [not her real name] was told she owed £44,800 for two months’ supply to her one-bedroom flat. “I’d been asked to send photos of my meters in August as Ovo believed there was an issue,” she said. “I did so and my account went from £600 in credit to £19,000 in debt. Despite Ovo assuring me this was a mistake, the debt rose to over £44,000 in September.” Her account was found to be £239 in credit after the Guardian contacted Ovo. The company admitted that meter reading errors have affected some customers, blaming problems with some accounts that were transferred to Ovo after it bought SSE’s retail division in 2020. The company blamed a mismatch between the opening and closing meter readings taken when Line’s SSE account was moved to Ovo and paid her compensation. Other customers told the Guardian that Ovo has continued to send implausible bills despite receiving updated meter readings and admitting errors. Jane Barclay’s projected quarterly energy consumption in her two-person household rocketed to £49,000 when she submitted meter readings. “I was assured my account would be put on hold but am now being chased over a bill of £34,015 for the three months to October,” she said. “What started as one of modern life’s irritations is now taking up many hours of my week and I’ve hit a brick wall trying to sort it out. I’ve cancelled my direct debit, otherwise they would have just taken the money, but I know that shortly they will put this in hands of a debt collector.” Ovo increased Alistair Strain’s monthly direct debits from £418 to £1,989 after calculating that he had used £23,330 worth of energy during July and August. His projected bill for 2023 was £29,000. “At least 12 separate customer services advisers have asked me for details, given assurances that our account would be put on hold and the matter resolved, but despite this, £1,989 was debited from my bank account last month.” Ovo admitted that meter reading errors have affected some customers who were transferred from SSE earlier this year. A spokesperson said: “We have processed millions of successful migrations to date, but we’re aware of a small handful of customers receiving large projections. To resolve this, our teams have set up an extra control to check for large bills to make sure we identify them, and fix them, before they’re sent to customers.” The company cancelled Barclay’s and Strain’s bills and offered compensation after contact from the Guardian. It has since refunded Strain’s direct debit payment, but he says his balance still shows a £21,000 debt and Barclay has yet to receive a correct bill. In 2020, Ovo was ordered to pay £8.9m in redress after the energy regulator, Ofgem, found it had wrongly charged customers over five years. Ofgem would not confirm whether it was aware of the latest charging issues when the Guardian alerted it to the shock bills. “Suppliers also have a duty to make sure customers receive the accurate final sum on their bill,” a spokesperson said. “We will assess this intelligence shared with us, and where action is needed, ensure suppliers are doing what is required of them to protect consumers during these very challenging times.”