“The power system is extremely constrained today and into the weekend, which will necessitate the use of open cycle gas turbines for most of today,” Eskom said in a statement.
“We anticipate that a portion of the capacity normally imported from Cahora Bassa hydroelectric power station in Mozambique will be unavailable on Sunday as the plant undergoes urgent planned maintenance.”
Rolling blackouts were scheduled from 6am to 10pm on Saturday and 8am to 10pm on Sunday.
City Power warned on Friday that Johannesburg would experience power cuts on Saturday and Sunday.
“Eskom has issued an alert to City Power indicating that they will be load shedding parts of the city on rotational bases,” the power utility said in a statement.
“This load shedding will not only affect the City of Johannesburg but affects the country as a whole, although on rotational bases.”
City Power said a schedule would be available on its website and it would update customers on its Twitter page.
Eskom said the electricity system would be constrained on Monday and Tuesday.
Emergency reserves would be used during evening peak times, but unforeseen technical problems at power stations or an increase in demand due to weather conditions could necessitate rotational power cuts.
“Load shedding schedules will only be utilised for the duration of the constraint,” it said.