Power utility Eskom has moved its power cuts from stage one to two, it announced on Twitter on Monday.
“Load shedding has moved from stage 1 to stage 2 as of 3pm,” Eskom tweeted.
Power cuts would continue until 10pm, it said.
Stage one allows for up to 1GW of the national load to be shed, stage two for up to 2GW, and stage three for up to 4GW.
“We do not know the reason why, we just received a call from Eskom to move to stage two,” Johannesburg City Power spokesman Sol Masolo said.
“Eskom managers are apparently in an emergency meeting,” he said.
Earlier, Eskom said the power system was severely constrained due to unforeseen technical problems at power stations.
It asked shopping centres and office blocks to switch off non-essential lights and put photocopy machines and computers on standby after hours, and for people to switch off geysers, air conditioners, pool pumps and all nonessential appliances. — Sapa