Power utility Eskom warned on Monday that unplanned breakdowns in its system could result in load-shedding at short notice.
"The system remains constrained and vulnerable, with generating plants performing at very low levels of reliability. With unplanned breakdowns at 9 100MW, the probability of load shedding remains, but will only be implemented if absolutely necessary," Eskom said in a statement.
"There is sufficient diesel for our open cycle gas turbines and water at the pumped storage schemes to supplement the shortage of capacity, if required."
The power utility said the situation was being monitored closely and appealed to consumers to use electricity sparingly to reduce demand.
Customers were also advised to check their load-shedding schedules on the Eskom or municipal websites.
"We remind customers that load-shedding is conducted rotationally as a measure of last resort to protect the power system from a total collapse or blackout. We will continue to keep South Africans informed about the status of the electricity system," Eskom said.