Ten energy suppliers have paid out around £7 million in compensation and refunds after an error led to some customers being overcharged, the energy watchdog has said. Industry regulator Ofgem said the compensation and refunds will have been paid out to more than 34,000 customers. It said this included more than 20,000 customers at the UK’s largest supplier Octopus Energy, which paid out £2.64 million in refunds and made a £546,278 goodwill payment. The error also impacted customers at Utility Warehouse, Ovo Energy, So Energy, Outfox The Market, Ecotricity, E.On Next, Tru Energy, Rebel Energy and EDF Energy.