<sod >In a statement on Tuesday, the company, which is owned by Centrica, said that the standard electricity tariff will go up by 12.5 per cent from 15 September.< eod>< sod > The company, which is owned by Centrica, said that it was leaving gas prices unchanged but that the standard electricity tariff will rise by 12.5 per cent from 17 September.< eod>