The ESB may not collect up to €4 million in arrears from 20,000 customers who pay for electricity through coin meters and who have been undercharged because their meters were not recalibrated to take account of price rises since 2001.
The company said it was currently engaged in a review of how its meters could be recalibrated to take account of future price increases.
It was also considering introducing meters which could be recalibrated electronically from head office.
Customers who pay for their electricity through meters, most of whom are on low incomes or have fallen into arrears in the past, have been undercharged by as much as 25 per cent in recent years.
This has led to fears among many customers that they will have incurred significant arrears which may affect their credit rating or even result in their power being disconnected. However, the ESB said neither would happen.
A spokesman said collecting the arrears would be "very difficult logistically". Each customer's case would have to be reviewed individually and arrangements to collect the money made with all of those affected if the money was to be collected.
Recalibrating all meters would take three to six months. Another price increase was planned for January and it would be "difficult to find a window of opportunity to recalibrate the meters between now and then," the spokesman said.
