Power utility Eskom instituted Stage 2 load shedding on Wednesday starting at 9:00. The national rotational power outages may last until 23:00.
Eskom said that it is experiencing a "shortage of capacity", and that more details will follow.
Stage 2 load shedding allows for 2 000 MW of power to be shed on a rotational basis. Stage 1 is the "lightest" load shedding schedule, while during Stage 4, up to 4 000 MW of power can be be shed.
Later on Wednesday, the utility said the rotational power cuts were due to a broken conveyor belt at Medupi, boiler tube leaks and low dam and diesel levels.
Eskom warned last month that plant maintenance which often takes place during the summer time may trigger outages.
"Most of our power stations are in need of maintenance to improve reliability... we do our best to strike the right balance between plant maintenance and keeping the lights on," said Eskom chairperson and acting CEO Jabu Mabuza.
South Africa last saw loadshedding in March this year, after a cyclone in Mozambique affected power imports from the country. Eskom also didn't have enough diesel to power its open cycle gas turbines.
#PowerAlert Due to a shortage of capacity stage 2 loadshedding is to be implemented from 9 am to 11pm today. Media statement with more details to follow @CityPowerJhb @City_Ekurhuleni @CityTshwane @CityofJoburgZA @CityofCT @ewnupdates @SABCNewsOnline @IOL @eNCA @SAgovnews— Eskom Hld SOC Ltd (@Eskom_SA) October 16, 2019
The energy availability of Eskom’s generation fleet is supposed to be as high as 80%, but was last month as low as 69%, an Eskom board member warned recently.
Even a 0.1% rise in economic growth could result in outages, Nelisiwe Magubane, an Eskom director, told an event last month.
A new plan to deal with Eskom, which will probably be split into generation, transmission and distribution units, is supposed to be discussed in cabinet today.
Earlier this week, President Cyril Ramaphosa said government will announce its plan to deal with Eskom's R450bn debt pile in the next days.
"I think Moody's and others will be happy with the announcements made," Ramaphosa said.
More than 270 hours of loadshedding contributed to South Africa’s economy shrinking by 3.2% in the first quarter of this year. While avoiding a recession in the second quarter, the economy has been struggling.
The rand weakened by almost a percent to R14.99/$ on Wednesday morning.
Compiled by Helena Wasserman