Stage 2 load shedding started at 21:00 on Saturday evening and will last until 05:00 on Monday, Eskom announced late on Saturday.
This is to replenish emergency generation reserves for the week ahead. Emergency generation typically involves using open-cycle gas turbines, which run on diesel. It is a very expensive way to generate power.
There have been breakdowns and trips at various power stations, as well as delays in returning units to service.
"This has required us to rely heavily on emergency generation reserves, which are now at very low levels. To ensure adequate reserves for the week ahead, it is necessary to preserve the remaining emergency reserves and to replenish as much as possible before Monday," Eskom said in a statement.
Over the past week there have been breakdowns and trips at Tutuka, Kriel, Hendrina, Kusile, Arnot and Kendal power stations. Some of the units have returned to service.
Total breakdowns currently amount to 15 627MW, while planned maintenance is 4 954MW of capacity. This means that almost half of Eskom's generation capacity is currently offline.
Load shedding last hit South Africa on October 14th.