Load-shedding will be increased to Stage 4 from 14:00 this afternoon until 22:00 tonight, after which it will revert to Stage 2, Eskom has announced.
It says this is due to additional breakdowns of a unit at Medupi and two units at the Duvha power station, together with the high winter demand, as well as to ration the remaining emergency generation reserves, which have been depleted.
"These emergency reserves are required to respond to further emergencies in order to maintain the stability of the national grid," it notes.
Breakdowns currently total 15 087 MW of capacity, while planned maintenance is 1 273 MW of capacity.
"These capacity constraints will continue for the foreseeable future and all South Africans are urged to reduce their use of electricity," Eskom warns.