Monday’s severe thunderstorms plunged many areas across Johannesburg into darkness.
City Power says the rains caused damage to electricity infrastructure, flooded transformer chambers and uprooted trees that fell on overhead cables.
It says the Main Delta Intake substation tripped due to an overhead line fault.
The outage is affecting several suburbs in the central, western, and southern parts of the metro.
Teams have been dispatched to investigate and repair.
The utility also says there has been a reported spike in electricity outage calls from frustrated customers.
It adds the number of complaints as well as damaged and flooded roads may delay response times.
City Power has apologised to customers for the inconvenience, and updates will be provided going forward.