The utility will start on several maintenance projects in the next few weeks that will take additional units offline, removing more than 2,300MW of generating capacity from the system, it said.
Koeberg 1 will be offline from 8 December until June 2023 for routine maintenance and refuelling.
"This loss of capacity, temporary as it is, will make for a very challenging summer season," Eskom's COO Jan Oberholzer said in a statement.
"We will have to continue limping along to meet demand for electricity, particularly over the next six to 12 months."
There have been 155 days of load shedding, since January, Eskom said. Large and small businesses and residential homes have borne the brunt of the power cuts, cited by policymakers as one of the major obstacles to economic growth.
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