The state-owned company, which is battling to keep the lights on in Africa's largest economy, on Thursday declared its second emergency in three months.
"We anticipate that the system will remain constrained for the rest of the day and next week," the utility said in a statement.
Eskom said earlier that it could declare another emergency should the system deteriorate. It declared the first emergency in five years in November.
The utility said it expected additional generating units to come back online and forecast lower demand ahead of the weekend.
Eskom provides 95 percent of the country's electricity.
Eskom urged its key industrial customers to reduce their usage by at least 10 percent to prevent rolling blackouts, known as "load shedding" in South Africa.
Most mines in the platinum industry are out of action due to a strike. Workers at Anglo American Platinum, Impala Platinum and Lonmin downed tools four weeks ago, demanding higher wages.
South Africa last suffered a power crunch in 2008 that forced the closure of mines, factories and smelters for days, costing the economy billions of dollars in lost output.