Eskom implemented Stage 5 from 4pm on Sunday.
The power utility says a generating unit each at Matla and Tutuka power stations broke down in the past 24 hours.
In addition, there has been a delay in returning to service of generating units at eight other power stations.
Eskom will reduce the blackouts Stage to 4 on Monday morning and back to 5 in the afternoon.
This pattern of switching us off between stages 4 and 5 will continue until further notice.