Stage 2 load-shedding will "regretfully" be implemented from 17:00 until 22:00 on Monday evening, Eskom said in a statement.
The previous bout of load-shedding was suspended just two days previously, on Saturday.
Earlier, Eskom said the power system had recovered sufficiently to meet the demand during the day.
"[But] Eskom would like to caution the public that load-shedding might be required at short notice during the evening peaks should there be further breakdowns in currently available capacity," the utility said.
Eskom had expected to return to service a generation unit each at Kusile and Kendal power stations before Monday evening. But it warned that should either of these units fail to return to service, there would be an "increased probability" of load-shedding at short notice.
The return to service of a generation unit each at Matimba and Lethabo, as well as two units each at Hendrina and three at Tutuka power stations, was also delayed, Eskom said earlier.