Power utility Eskom warned on Friday morning that if protests at nine of its power stations and facilities continue, it increases the risk of higher stages of load-shedding.
SA is currently experiencing Stage 2 load-shedding every day up to midnight until Sunday.
"These protests included incidents of intimidation of working employees and blockading of roads leading to power stations and other facilities, inhibiting the free flow of personnel and commodities required for the generation of electricity and smooth operations," Eskom said in a statement.
"The increased unavailability of plant has necessitated an extensive usage of emergency generation reserves, which are depleting faster than can be replenished.
"Eskom cautions the public that should these criminal acts of intimidation persist or spread, this would increase the risk of operational disturbances and the implementation of load-shedding at higher stages."
Eskom reiterated that the provision of electricity is an essential service, and industrial action is not permitted.
"Eskom appeals to its labour partners and striking employees to embrace the higher purpose of putting the people of South Africa first, respect the law and to desist from illegal and undemocratic conduct."
In May, the National Union of Metalworkers of SA (Numsa) demanded a 15% wage increase across the board, which Eskom management maintained it could not afford.
On Wednesday Eskom confirmed that it reached a deadlock in talks with Numsa the at the Central Bargaining Forum.
Eskom general manager for people relations Thulane Ngele said at a briefing that parties could refer the matter to the Commission for Conciliation, Mediation, and Arbitration (CCMA).
Numsa alleged in a statement that Eskom collapsed the talks because it did not want to be held accountable for spending on coal and Independent Power Producer contracts.