Eskom will start power cuts from 9am on Thursday, a spokesman confirmed.
“There will be load shedding in different suburbs across the country,” said Eskom spokesman Andrew Etzinger.
He said it was likely to continue until 10pm.
Municipalities were informed of the need to reduce electricity and they would decide in which suburbs to cut power.
Etzinger could not say if power cuts would affect the Oscar Pistorius murder trial in the high court in Pretoria. He said the Tshwane municipality would be in a better position to comment on that.
Earlier on Thursday, Etzinger said seven days of heavy rain had left coal stocks wet.
“We have asked our large industrial customers, to reduce their consumption by 10 percent, but it appears this will not be enough,” Etzinger said. — Sapa