Cape Town - Eskom said on Friday due to increased electricity demand and a shortage of generation capacity it will implement stage 1 load shedding from 12:00 to 17:00 and stage 2 load shedding thereafter.
Stage 2 load shedding is likely to continue until 22:00.
The power utility warned that any unexpected changes on the already vulnerable and constrained power system could lead to a change in the load shedding stage at short notice.
Eskom said on Thursday unit 2 of the Koeberg nuclear power plant outside Cape Town will be shut down for three months from the end of August as part of routine refuelling and maintenance.
In February, unit 1 of the plant was shut down for a similar period, resulting in the loss of half the output at the 1 800 megawatt nuclear power plant.