Eskom announced on Sunday evening that stage 2 rotational power cuts would continue overnight and all day on Monday. The struggling power utility said it expected load-shedding to stop at 23:00 on Monday.
There is a high likelihood that power rationing will be implemented for the rest of the week.
Stage 2 allows for up to 2 000MW - just under 5% of Eskom's nominal capacity - to be cut from the national grid.
The utility was hoping the use the weekend to fix unplanned outages of generating units, but said on Sunday evening that additional units had been lost. Unplanned breakdowns were at above 12 000MW on Sunday evening, about a quarter of the utility's nominal generating capacity.
Eskom said it would be implementing load-shedding overnight to enable it to replenish water supplies for its pumped storage schemes, which it hopes will help lessen the impact of cuts during the week.
"We continue to ask customers to reduce demand as a concerted collective effort to avoid or lessen the level of load-shedding," it said.