The power grid is under severe pressure after two generating units that can generate a total of 1,300 MW have been eliminated, Eskom warns.
The utility company says a unit at Medupi near Lephalale in Limpopo and at Tutuka near Standerton in Mpumalanga broke down early last night.
Eskom is calling on South Africans to turn off all unnecessary devices to try and save power.
The risk of load shedding will continue until after the weekend, according to the statement. Eskom teams are working hard to correct the errors, according to a statement.
Over the past weeks, Eskom has been warning every night at 18:00 of pressure on the network, through probably a scheduled tweet. This is followed by a tweet at 21:00 that reassures consumers that the pressure on the network has been alleviated.
Chief executive André de Ruyter said earlier in parliament that they only provide three days of load shedding this winter, probably in July.
South Africa last experienced shedding in March.
The Covid-19-related restriction has significantly lowered the demand for power.