Load shedding is set to continue at stage 2 until 23:00 on Saturday night, Eskom said on Friday night.
It would be required overnight and all day on Saturday to cater for further trips and to create capacity to replenish water reserves for pumped storage schemes, Eskom said.
Unplanned breakdowns continued above 12 000 MM, the power utility added, requiring the use of diesel and water reserves for open cycle gas turbines and pumped storage schemes. Later on Saturday, it said it had made "some progress" in reducing unplanned breakdowns from above 12 000MW on Friday to 11 000MW early on Saturday.
"There is also an improvement in managing coal handling with regard to wet coal," Eskom said.
It had earlier said wet coal had contributed to the problem.
"With the incessant rain, we continue to experience coal-handling problems at a number of our power stations as a result of wet coal, which has led to generation units being unable to produce power," Eskom said.
Energy analyst Chris Yelland told Fin24 on Friday that wet coal is typically more of a problem when coal reserves are low.
In its statement, Eskom said stage 4 load shedding was "no cause for alarm". It added that load shedding was implemented to prevent total collapse of the system.