The energy regulator fined the firm for wrongly reporting data between the period of 2010-2013 regarding its Renewables Obligation (RO) scheme and Feed-in Tariff.
The RO scheme relates to power companies sourcing a set amount of electricity from renewable energy sources, whereas the Feed-in Tariff is designed to encourage energy firms to provide incentives to small-scale renewable energy generators via cash payments.
In both cases npower was found guilty of under-reporting the amounts by 0.08% between 2010-2011 and 0.28% between 2011-2012, although the energy supplier did identify the issues itself according to Ofgem.
npower CEO, Paul Massara, said the firm discovered the issue during work to increase its controls around compliance reporting.
He said: "Accurate reporting is extremely important to us – especially in areas of compliance – and we have assured Ofgem that the changes we have made to our controls and procedures will ensure this error does not happen again."
Ofgem considered the fact the firm reported the issue when issuing the fine it declared.
In a statement it added: "The size of today's penalty takes into account that npower has already voluntarily forfeited Renewable Obligations Certificates valued at £896,900 and will make a late payment of £63,000 to account for the FIT reporting error."
The fine comes less than a week after fellow 'Big Six' energy supplier E.On was hit with a record £12m fine for misrepresentation and mis-selling of energy tariffs to customers over the phone and via door to door sales between June 2010 and December 2013. Npower itself was hit with a £3.5m fine last December in a similar case.
In the last four years Ofgem has now issued out fines and redress upwards of £100m to energy suppliers for various rule breaches - £39m of which is purely down to the mis-selling of energy tariffs.
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