Power has been restored to all parts of Northern Ireland tonight after earlier cuts hit tens of thousands.
The widespread power cuts happened when one of the North's main power stations stopped generating and another could only provide a reduced level of electricity.
Operational problems at the Ballylumford and Killroot power stations in Co Antrim - with Killroot completely out of service - meant there was not enough electricity to meet customer demand, said NIE.
A spokesman said a combination of a reduction in demand, Kilroot managing to produce some electricity and an increase in the electricity sent through the undersea interconnector from Scotland was meeting demand.
The company said it did not anticipate any further power cuts. Northern Ireland enterprise minister Mr Ian Pearson called for a swift report from NIE.
After speaking with company's managing director Mr Harry McCracken, he said he had been assured that what had happened had been extremely rare and the matter would be thoroughly investigated.
PA