Eskom said in a statement it unexpectedly lost four large units due to unplanned breakdowns.

"The breakdowns happened at a unit at Kendal, Majuba and Lethabo power stations," Eskom said.

"Furthermore, a unit at Duvha and Tutuka power stations have not returned to service as expected."

It said another unit at Kendal was taken off due to technical difficulties.

"Eskom has 31,000MW available total capacity to meet tonight (Tuesday).

"While we expect some units to return to service soon, the situation may persist until the weekend."

Meanwhile, parts of Gauteng will experience what Eskom calls "load reduction" until 10pm. 

Areas affected include Soweto, Roodepoort and the Vaal.

eNCA