Power utility Eskom on June 23 appealed to the public to reduce electricity consumption, warning that the generation system was severely constrained.
"We have unexpectedly lost four large units to unplanned breakdowns, while the return to service of another two generation units has been delayed. The breakdowns happened to a unit at Kendal, Majuba and Lethabo power stations. Furthermore, a unit at Duvha and Tutuka power stations, have not returned to service as expected," it said in a statement.
It added that a further unit at Kendal had been taken off owing to technical difficulties and to address emissions.
"While we expect some units to return to service soon, this situation may persist until the weekend.
"We urge the public to reduce consumption by switching off non-essential appliances in order to maintain the integrity of the system," it said.