ESB Networks is advising households and businesses that they are working to resolve an issue which caused some smart meter readings to be processed incorrectly last week.
It has apologised for the "confusion and concern" this may have caused and said they are reviewing their processes to ensure this does not happen again.
It follows reports of numerous electricity customers highlighting significant price hikes on their meters in recent days, with some as high as €5,000 for one day.
Many customers took to social media to reveal the "impossible" and "wild" costs on their smart meters on 6 and 7 March.
One Bord Gáis customer described how on 5 March his meter read 4.18 kW use for the day at a cost of €1.83. While the next day the cost rose to €738.
Another person said their meter showed they had used 7000kW in one day at a cost of €2,500.
Customers also said they had been assured by their suppliers that it is a "known issue" that is being fixed this week and that no action is required from them.
ESB Networks has since explained that last Friday a planned software upgrade to one of their internal systems caused some customers' meter readings to be processed incorrectly, resulting in high and incorrect usage on ESB Networks online accounts and on those of suppliers.
In a statement, it said it is an internal software issue and is not related to the integrity of smart meters or the recorded energy use.
"We are in the process of identifying and resolving the issue in our systems and will systematically correct all affected data."
It said customers do not need to do anything at this stage and will automatically adjust metering data to reflect actual usage.
Bord Gáis Energy said that following the issuing of incorrect meter data, it took action to switch off billing for associated meters to minimise the impact on customers.
In a statement, it said: "We are awaiting updated data from ESBN [ESB Networks]. We will resume customer billing once correct data is received."
SEE Airtricity said it is aware of the issue and added "our team is working on it. While we fix it, you don't need to do anything. Thanks for your patience. We apologise for any inconvenience".
It is estimated that there are around two million smart meters installed across Ireland.
The Commission for Regulation of Utilities said it is aware of the issue and it is engaging with ESB Networks in relation to the matter.
"Our understanding is that ESBN has resolved the issue and are working to amend any incorrect data showing on customers' accounts. We would note that the issue is not with the smart meters themselves and that they are functioning as normal.
"ESBN are liaising with suppliers to address any queries they have. We would encourage customers to engage with their supplier directly if they have any questions about their bills," it said.
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One year's worth of energy in one day
Daragh Cassidy, Head of Communications at Bonkers.ie, said he got a shock when he checked his smart meter account recently, as it showed he had used over one year's worth of energy in one day.
"I am not the only one who has been impacted. It seems to have affected tens of thousands of smart meter customers throughout the country. For a lot of people that is going to have caused anxiety, particularly those who were due to get a bill over the next few days. I think they will be worried or anxious that they are acutally going to be charged for the consumption and I hopeful that is not going to be the case and that it is really just a systems error."
"I think the energy suppliers or EBS Networks should issue a statement to clarify that anyone who was due a bill over the next few days isn't going t be charged for that consumption."
He said some of those bills would be over €5,000 which many would not be able to afford.
Mr Cassidy said people will reflect on the reliability of smart meters following this issue. He said it also shows people are actively monitoring their consumption to see how much energy they are using. "That is absolutely a positive."
He said while what happened gave people a fright, he believes generally smart meters are a valuable benefit and can help people reduce their bills in the longer term.
