Eskom warned on Friday that the risk of scheduled power cuts had risen to "Stage 2" as the electricity grid came under strain.
"There is a high probability of Stage 2 rotational loadshedding from 09:00 until 22:00 today as a result of loss of additional units overnight," the power utility said.
Stage 2 loadshedding means 2 000 megawatts of power are taken off the grid nationwide to prevent collapse of the system.
Eskom implemented Stage 1 loadshedding on Thursday.
It has warned that the country will likely see more planned outages for the remainder of the year.