Electric Ireland is going to payout €13m in compensation to customers who it overcharged across a five-year period when it miscalculated how much it should be billing customers for a levy on electricity bills.
It overcharged for its Public Service Obligation (PSO) charge between 2008 and 2013 - this fund is used to provide guaranteed prices for energy from wind farms.
Electric Ireland flagged this issue with energy regulators and it emerged that it had charged €12.97m too much - the regulator ruled that the overcharged sum should be repaid with interest, pushing the total amount to be paid out to over €13m.
Affected customers will be repaid over the next 12 months through a reduction in the PSO payment charged on their bills.
The Commission for Energy Regulation admitted to the Irish Independent that PSO payments had "scope for misinterpretation" - although no other electricity provider had made the same mistake.
The electric company has not accepted that it did anything wrong - but it welcomed that the regulator has brought "clarity" to the situation.
It continues, "This rebate in itself will mean a reduction of approximately €2 in the annual PSO charge for a residential customer (or 33c in the typical two monthly bill) for the next 12 months."