Eskom has implemented stage one of rolling power cuts from 2pm to 10pm, it said on Wednesday.
“If there is a need to move into stage two, we will communicate accordingly,” its media desk said in a statement.
This was due to a shortage of generation capacity as several units were currently out of service due to planned and unplanned outages.
The power system remained severely constrained and would be for the rest of the week, it said.
Eskom was focused on returning the units that were on unplanned maintenance back on line in order to increase available capacity.
“As temperatures hit highs in the past few days, we would like to thank all the customers who responded to our call and reduced their energy consumption, including keeping air conditioners at 23°C,” it said.
Earlier, spokesman Khulu Phasiwe urged citizens to switch off all non-essential appliances.
Eskom had found that some municipalities were leaving street lights on during the day. Some people were also leaving their house lights on.
“Street lights need to be switched off during the day,” said Phasiwe.
During stage one blackouts 1000MW of the national load is cut, 2000MW during stage two, and 4000MW in stage there.