Eskom said there was a risk of stage 1 load-shedding from 2pm to 10pm on Thursday.
The power utility said the load-shedding was as a result of a shortage of generating capacity.
On Wednesday evening, Eskom warned that the power system remained tight and said it was possible that it could lose additional power-generating units.
On Wednesday evening, it requested customers to use electricity sparingly.
Eskom said load-shedding was done countrywide as a controlled option to respond to unplanned events to protect the electricity power system from a total blackout.
Stage 1 allows for up to 1,000MW of the national load to be shed.
"While the risk remains high, load-shedding will only be implemented if absolutely necessary. We remind customers that load-shedding is a controlled measure which protects the power system from a total collapse or blackout," Eskom said in a statement.
Eskom encouraged customers to continue to use electricity sparingly.
"Please switch off geysers, pool pumps as well as all nonessential lighting and electric appliances to assist in reducing demand."
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