Load-shedding was moved from stage 2 to stage 4 on Tuesday afternoon after a power station unit at Koeberg tripped.

Eskom said on Monday that it would continue implementing stage 1 load-shedding until Tuesday morning, but would then increase it to stage 2 from 9am.

But just a few hours later, the embattled power utility announced the increase to stage 4.

Following the breakdown at Koeberg, the unit was disconnected from the grid. Eskom said the fault was on the turbine side of the plant and the nuclear reactor was safe.

"The teams are investigating the root cause of the fault and will advise on the remedy as soon as it is established." 

It added: "As the ageing fleet is constrained, unpredictable and vulnerable, we advise South Africans that the stage of load-shedding may change at short notice should there be any unexpected change in the generation system performance."