Eskom will implement Stage 4 load shedding from 12:00 on Saturday.
According to the power utility, this is due to a loss of 900 MW imports from Mozambique.
Earlier on Saturday morning the power utility said it would be implementing Stage 2 load shedding from 08:00 to 23:00 due to a shortage of capacity and a loss of additional generating units. But just after 10:00 the power utility alerted consumers via Twitter that load shedding would be kicked up to Stage 3.
"The situation remains tight and volatile and we may have to implement further load shedding should the situation deteriorate," Eskom said in a statement.
"Depending on how quickly we can restore power, this may impact the prognosis for tomorrow and next week," the power utility warned.
Eskom has said load shedding is a "highly controlled process" to avoid a complete blackout.
According to Eskom, at Stage 4 load shedding, 80% of the country's electricity demand is being met, as only 4 000 MW is being load shed on a rotational basis.
If there is a need to go beyond Stage 4 load shedding, Eskom and municipalities will implement contingency schedules. "Even beyond these schedules, the System Operator will reduce demand in a manner that is controlled but unscheduled," Eskom said.
On Saturday afternoon Canal Walk Shopping Centre, in Cape Town, sent out a tweet indicating a zone in the mall would be affected by Stage 4 load shedding.
The mall is relying on generators to keep essential services running. Canal Walk said most of the bigger stores are still trading.