After some of Eskom's generating units failed over the weekend, SA's power supply was running dangerously low by Wednesday morning.
The power utility is now battling an electricity shortfall of 12 000 MW due to these breakdowns as well as unplanned maintenance.
In a statement issued on Wednesday morning, Eskom said that while some of the units are back online, along with others that have been down due to scheduled maintenance, they are not generating sufficient electricity to meet current demand.
Unplanned outages above 9 500 MW mean Eskom has to resort to emergency power generation by using open cycle gas turbines and pumped-storage hydroelectric plants. These are very expensive ways of generating power, particularly the gas turbines, which require large quantities of diesel. They can only be used for short periods before diesel and water reserves start running out.
"Eskom has since Monday increased its usage of its pumped storage and diesel generators to keep the lights on. The extensive use has led to a decline in pumped storage water and diesel levels and a concerted effort is being made to replenish these reserves," the utility said.
Its emergency response command centre is now trying to supplement diesel to "avoid and/or if unavoidable, minimise load shedding".
"The probability of load shedding remains and any shift of the system could result in load shedding at short notice," it said.
It advised customers to check their load shedding schedules. An update on the power situation will be provided later on Wednesday.
Reuters: "S. AFRICA'S ESKOM SAYS POWER SYSTEM REMAINS SEVERELY CONSTRAINED THIS MORNING WITH UNPLANNED BREAKDOWNS ABOVE 12 000 MW"— John Ashbourne (@JohnAshbourne) November 6, 2019
For context, Eskom's total generating capacity is 44,000 MW, so about 27% of the total system has broken down.
Eskom urged customers to use power sparingly, by setting air conditioners' average temperature at 23 degrees and switching off geysers.
Last month, South Africans suffered five days of load shedding after outages at five generating units. Eskom also resorted to emergency power generation, but when its diesel stocks started running low, it was forced to implement rotational power outages.