Power utility Eskom on Wednesday called on consumers to switch off geysers, pool pumps and all non-e.
Yesterday metal workers union Numsa and teachers union Sadtu proposed but failed to persuade the congress to discuss ANC leadership.
Cosatu general secretary Zwelinzima Vavi said the matter had been referred to the labour federation's central executive committee and could not be discussed at the congress.
Earlier ANC secretary-gen eral Gwede Mantashe gave the strongest indication that he supported Zuma for a second term as ANC leader.
Mantashe seemed to be campaigning for Zuma when he referred to a "Zuma moment" instead of a "Lula moment'' as called for by Cosatu.
He said a "Zuma Moment" could be achieved with Cosatu's help, particularly in ensuring that agricultural land was optimally used for production.
Lula is the former Brazilian president who, in his second term, became popular for introducing radial economic policies that reduced inequality, poverty and unemployment. Cosatu is proposing that the government take the same direction.
"We agree with the thrust of Cosatu's central executive community socioeconomic document but we want to add a few issues and their contribution to make the Zuma moment a reality.
"Cosatu must join the ANC in working out what minerals should be nationalised as the discussion will be key in Mangaung," Mantashe said during the discussion on the socio-economic policies to be adopted by the labour federation.
Earlier, delegates showed deep divisions over whether to support Zuma or his deputy Kgalema Motlanthe ahead of the ANC's elective congress in December.
While some affiliates attending the last day of the congress broke into pro-Zuma songs accompanied by hand signals endorsing his bid for a second term in office, others revolted, calling for change using substitution signs like those used at soccer matches.
About two groups marched around the hall, trying to outdo one another.
The general secretary of the National Union of Mineworkers, Frans Baleni, seemed to make it known whose camp he was in as he held up the V-sign, together with the Cosatu president Sdumo Dlamini, who danced on stage, next to federation general secretary Zwelinzima Vavi.
There were also opposing positions among members of the National Union of Metalworkers of SA.
Some of them loudly shouted "sifuna uKgalema" (We want Kgalema), while their counterparts sang Zuma's praises.
One member danced on top of a table holding a framed photograph of Motlanthe.
Vavi took to the podium and warned that the showing of signs was divisive to the congress.
Meanwhile, Cosatu has declared Aurora mining, which is owned by Zuma's nephew Khulubuse, the worst performing company.
Hand signals used to show support for Zuma or Motlanthe