Eskom is implementing stage three rolling blackouts, it announced on Friday.
At 12.22pm the power utility tweeted: “Eskom has implemented Stage 3 load shedding. ow.ly/i/7PC5u.”
Eskom said it would release a statement on Friday.
On its load-shedding website, it said rolling blackouts would be used “under emergency conditions for limited periods”.
It said three schedules had been developed, based on the possibility of risk and to ensure it was applied fairly and equitably.
Stage one allowed for up to 1000MW of the national load to be shed, stage two for up to 2000MW and stage three for up to 4000MW.
On the website, it said load-shedding would generally be implemented in two hour blocks, plus 30 minutes for switching between blocks, from 5am to 9.30pm.
On Thursday, Eskom said it was planning countrywide power cuts over the weekend to build up reserves.
“The electricity system will remain constrained tomorrow [Friday] and the risk of load-shedding remains high,” it said.
On Friday, the City of Johannesburg and City Power said it would remotely switch off geyser control systems to certain areas to manage electricity control across the city.
The city also appealed to its “large power users and key business customers” to reduce their usage of electricity by switching off non-essential machinery and appliances such as air conditioners and lighting.
“City Power also requests domestic customers and medium and small enterprises to reduce their electricity consumption by switching off non-essential appliances, such as office and basement lights, where possible.”
Eskom said on Thursday that the electricity system would be under severe strain at the weekend, and it asked municipalities to reduce demand by cutting power to their customers.
City Power and the City of Johannesburg said customers should visit their websites to confirm the rolling blackout schedule, and should have torches and lanterns at hand to light up their homes.
The Nelson Mandela municipality said rolling blackouts started in the area at 11am.
In a statement, the municipality said it was highly probable there would be blackouts over the weekend. SAPA