Opting for staggered power cuts was a painful move but unavoidable to save the electricity system, Eskom CEO Brian Dames said on Friday.
"The decision was necessary to avoid a total black-out," he told reporters in Johannesburg.
He said a total black-out would have had significant consequences for the South African economy.
Eskom was committed to providing early warnings, and the warning on Thursday was the earliest possible, he said.
"This was the earliest we could communicate as the system status changed rapidly on the morning of March 6."
He apologised to the public for the inconvenience caused by the power cuts. Power cuts had ceased countrywide from 10pm on Thursday.
"If there are still any... robots not working or power cuts it's because of local suppliers."
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