Eskom said it would not be able to suspend load shedding during the peak traffic period on Tuesday afternoon.
The power utility resumed stage one power cuts at 9am which are expected to continue until at least 6am on Wednesday morning.
Eskom warned that the blackouts were likely to continue for the next 18 months while critical maintenance was being carried out on its aging infrastructure.
Stage one load shedding is being implemented on Tuesday, with an update on the situation expected later.
Eskom spokesperson Sikonathi Mantshantsha said: “We will not be stopping load shedding between 4pm and 6pm – the reserves don’t allow [that for] the system right now.”