Power utility Eskom has announced that it is implementing stage 3 load shedding from 13:00 on Wednesday to 06:00 on Thursday morning.
There is a high probability that load shedding will continue into the rest of Thursday.
It said the cuts were necessary due to high-generation unit breakdowns over the past three days, and the need to replenish "diminishing emergency generation reserves".
"This morning, a generation unit each at the Lethabo, Kendal and Duvha power stations were taken offline for repairs, adding to the high number of breakdowns and units that have failed to return to service as planned," the power utility said.
Wednesday's announcement follows stage 2 load shedding that was implemented from Tuesday night until Wednesday morning.