Eskom will implement stage-2 national load shedding from 9pm on Thursday evening. The rolling blackouts will continue until 5am, the state-owned utility said.

The cuts are necessary to replenish emergency generation reserves, it said in a statement issued at 6pm. They will resume again on Friday at 9pm and will continue until 5am on Saturday.

The emergency reserves were depleted during business hours to keep the lights on.

“Emergency reserves have been depleted faster than expected due to further breakdowns of a generating unit each at Kriel and Tutuka power stations today,” Eskom said.

“Delays in returning generating units at Tutuka, Grootvlei and Kendal have also contributed to the depletion of emergency reserves.”

Total breakdowns amount to 15GW, while planned maintenance is 5.3GW of capacity, it said.

“Should the emergency generation reserves not recover sufficiently, it may be necessary to continue load shedding during the day and over the weekend. Eskom will communicate promptly should there be any significant changes to the power system.”