Eskom has warned in its second power alert of the day of a "high risk" of stage 1 rotational power cuts until 22:00 on Tuesday.
"[The cuts] will only be implemented if absolutely necessary," it said in a statement. "This is as a result of a shortage of capacity due to the loss of generating units at our power stations".
It did not provide further information.
Stage 1 load shedding allows for up to 1000 megawatts to be cut from the national grid.
In its initial alert at lunchtime the power utility had gauged the likelihood of rotational power cuts as "medium" and urged consumers to turn off all non-essential appliances.