TimesLive reported on Thursday that Johannesburg City Power employees went on strike late on Wednesday afternoon.
City Power spokesperson Louis Pieterse told the site that a about 200 workers went on strike. "They worked during the day and downed tools at 4pm, saying they won't work after hours," he said.
Pieterse said the cause of the dispute was that City Power was in the process of introducing shifts to its work rosters to improve service delivery, which some employees did not agree with.
He added the shift roster was required was because workers were sometimes needed to attend to outages after normal working hours.
"Unfortunately, there is a certain level of resistance by some employees which has resulted in unlawful work stoppages," TimesLive quoted him as saying.
The workers were striking on their own and not under a union, the site reported.
Meanwhile, several areas in Johannesburg were without power, which Pieterse said was not caused by anything serious.
"We are experiencing some delays in response times and restoration times … Contractors have been appointed to restore the power," he told TimesLive.