Eskom will implement stage 4 load-shedding from 2pm.
The embattled power utility's spokesperson, Nto Rikhotso, confirmed to TimesLIVE at 12.30pm that stage 4 would last until at least 6am Saturday morning.
"Available capacity has gone down, and demand has increased," she said.
Explaining the reasons for the upgrade from stage 2 - which started at 4pm on Thursday - she said: "Last night [Thursday] we implemented load-shedding because we wanted to augment water resources. Some of the units we expected to come back [online], did not come back.
"Further to that, this morning [Friday], because of the rain, we are starting to experience coal-handling issues because some stations now have wet coal, and thus more units are not able to generate," said Rikhotso.
She said that should the situation change, it would be communicated to the public.