Despite successfully returning four generation units to service, Eskom on Thursday has said this will not stave off load-shedding and has announced that it will continue to implement Stage 2 load-shedding until 10pm on Thursday and between 8am and 10pm on Friday.

"This load-shedding has been caused by an increase in plant breakdowns over the past few days. Staying on Stage 2 load-shedding will also assist us in preserving our emergency generation reserves, namely diesel and water," the power utility said in a statement.

"Today Eskom teams successfully returned a unit each at the Matimba, Kusile, Tutuka and Kriel power stations," Eskom said. 

"The delay of the return to service of a unit each at Duvha and Tutuka and the breakdown of two units at Kriel, and a unit each at Tutuka and Kendal power stations have resulted in the need for load-shedding today."

It said that breakdowns in the past week had removed more than 13 500MW (mega watts) of capacity from the system, while planned maintenance was 5 000MW of infrastructure.

Eskom says that while it is working hard to return as many of its generation units to service, the "generating plant continues to perform at low levels of reliability, any unexpected shift such as an increase in unplanned breakdowns could result in a change in the load-shedding stage at short notice".

Calling on the public to continue to reduce electricity use, the power utility says that supply constraints may persist over the weekend. "We urge the public to continue reducing electricity usage to help us minimise load-shedding. 

"Eskom wishes to assure the public that implementing load-shedding is the last resort, in order to protect the national grid. We will communicate should there be any significant changes to the supply situation," the power utility said.