South Africa's Eskom said it would implement "Stage 2" power cuts between 1600 and 2400 local time (1400 and 2200 GMT) on Saturday and Sunday due to several generating units breaking down and delays returning others to service.
The struggling state-owned company resumed power cuts on Wednesday after a pause of 11 days, and implemented them again on Thursday and Friday.
Last month weeks of regular outages prompted public anger and prompted President Cyril Ramaphosa to make new pledges to tackle the crisis.
Eskom's power station fleet comprises mainly of coal plants that are highly prone to faults.
A record amount of electricity is set to be cut from the national grid this year, constraining economic growth in Africa's most industrialised nation.
Stage 2 outages require up to 2,000 megawatts to be shed from the grid.