Eskom will start rolling blackouts countrywide at 4pm today because of low diesel reserves, the parastatal said.
"Unfortunately it is necessary to implement stage two load shedding from 4pm to 10pm," spokesman Andrew Etzinger said.
"Diesel reserves... are basically depleted and we are therefore experiencing a difficult situation."
Diesel was needed to run the open cycle gas turbines. These were power stations which used diesel to generate power.
Etzinger said the current demand for electricity was higher than Eskom's capacity.