Eskom says it will implement load reduction on Saturday evening to avoid damage to infrastructure caused by overloading.
Power supply interruptions will affect various "high-density areas in Gauteng, Limpopo, Mpumalanga and KwaZulu-Natal provinces between 17:00 and 22:00.
"Eskom is battling to keep up with the increased equipment failure caused by overloading that is costing millions to repair," the power generator said in a statement.
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The power utility had earlier on Friday said it did not expect to implement loadshedding over the weekend, as its three generating units had returned to service.
Compiled by Sibongile Khumalo