Eskom was expecting its system to remain constrained on Friday and next week, it said.
“We anticipate that the system will remain constrained for the rest of the day and next week, with a slight reprieve over the weekend,” said spokesman Andrew Etzinger in a statement.
Electricity users were urged to keep usage reduced throughout the day.
“We are working hard to increase our reserve margin by ensuring that we have adequate emergency reserves, including water, coal and diesel supplies.”
He said their technicians were working to return generating units which were primarily out of service due to mechanical failures.
Eskom declared the power emergency on Thursday afternoon, urging major industrial customers to reduce electricity consumption by at least 10 percent.
“There were noticeable savings on Thursday evening as industrial, commercial and residential customers contributed approximately 1000MW of savings. We thank all our customers who reduced their load.”
He said key industrial customers were able to go back to full production by 9pm.
Shopping centres and the retail industry were also urged to contribute towards saving electricity by switching off geysers and adjusting air-conditioning temperature levels.
“We also ask that workers switch off lights, with the exception of the security lighting, when they leave office buildings in the evenings and that they please avoid leaving on air-conditioning overnight.”
Etzinger called on residents to switch off geysers, air conditioners, lights and non-essential appliances.