The utility, which operates an aging fleet of faulty coal-fired power stations, said it was increasing the level of power cuts due to breakdowns at some of its plants.
Stage 6 requires up to 6,000 megawatts (MW) to be shed from the national grid. It is the highest level of power cuts ever implemented in South Africa and means at least six hours without power a day for many South Africans.
"This is due to a high number of breakdowns since midnight, as well as the requirement to strictly preserve the remaining emergency generation reserves," Eskom said in a statement.
Last month Eskom warned it would continue to struggle to meet power demand in the next year.
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