After instituting rotational power cuts overnight, Eskom announced on Friday morning that stage 2 load-shedding would again start at 09:00 and continue until 06:00 on Saturday morning.
Stage 2 load-shedding allows for up to 2 000 MW to be cut from the national grid.
The utility, in an update on Friday morning, said that unplanned breakdowns were still above 12 500 MW, about a quarter of its nominal generating capacity.
It said its technical teams had been unable to return units to service from planned maintenance or unplanned outages. This meant it had been unable to replenish water reserves overnight for pumped water storage schemes, which it said contributed to the need to institute cuts on Friday.