Sipho Neke of Eskom's media office blames the blackouts around the country on "an unpredictable situation".
The South African Chamber of Business (Sacob) warns that Eskom is hammering the economy and ordinary citizens are having to learn how to adjust their lifestyles.
Monalisa Sam, manager of Maponya Mall in Soweto, said that Eskom's load-shedding had kept shops in the dark for extended periods at least twice a day for the past few weeks.
"Usually after noon there are power outages that can last between two and two-and-a-half hours," he complained.
Eskom is compelled to cut power, in what it euphemistically calls load shedding, as it simply cannot generate enough electricity to meet the demand of South Africa's thriving economy.
Though Eskom provides a load-shedding schedule on its website, Sam said it is often inaccurate.
Neke said when demand unexpectedly exceeds supply there is no time to warn businesses and consumers that "pregenerated schedules" will be implemented.
Businesses, big and small, have suffered the consequences.
Nothando Sibaya of Good Luck Butchery in Jabavu, Soweto, said they have been affected.
"The most has been twice a day. The electricity will go away and come back only to go away in two hours time," she said.
Butchers around the country have had to destroy tons of meat that rotted in the heat.
Cees Bruggemans, First National Bank's chief economist, said all South Africans will have to learn to adapt until Eskom can bring new power stations online in five to eight years.
Bruggemans and Bill Lacey of Sacob blame the government for failing to avert the situation.
Lacey said Eskom can do very little about the situation. Mbeki's government refused to fund expansion plans 10 years ago.
Now Eskom finds that demand exceeds supply when it shuts power stations down for regular maintenance or when they experience technical problems.
Thembani Bukula of the National Energy Regulator of South Africa (Nersa) said that the regulator opposes load shedding, and that additional generating must be added.
But it takes eight to 10 years from planning to the time a big power station is added to the national electricity grid.
Neke said the load-shedding system would be revised in consultation with municipalities. Eskom's regional boundaries are not the same as municipal or residential boundaries.
Most big hospitals have emergency generators that kick in when the power is cut, but Eskom and municipal electricity utilities have tried to shield them from outages.
The Chris Hani-Baragwanath and Helen Joseph hospitals in Johannesburg said on Friday that they had so far escaped power cuts.
Lacey said Sacob was talking to the government about the cost of generators.