South Africa's energy woes are a "challenge", but not a crisis and the government knows how to address it, President Jacob Zuma said on Friday.

"I think we have a challenge, not a crisis," Zuma told a breakfast meeting in Cape Town the morning after he announced a R23-billion cash injection for Eskom.

The president again blamed the scheduled blackouts, in part, on the apartheid regime's failure to expand the electricity supplier's capacity.

"If you look at energy, energy has a history in this country, it has never been enough. It was believed to be because the powers that be at the time said 'we have enough'."

"So the demand has just rocketed after 1994, and therefore undermined the capacity we have."

Zuma added that he was concerned about shortcomings in the running of the power grid and the government wanted to establish whether this was due to negligence.

"You can't have one power station collapsing after the other because they are not serviced. Where were the people who are working there? What were they doing?"

But he said the government believed it could resolve the capacity constraints that had seen Eskom increase load shedding in recent weeks.

"We have a plan for dealing with the matter. It is a good plan, great plan, and we are financing it. So it is not like we don't know what to do."

Asked to forecast how the South African economy would be faring in a decade, Zuma said he believed it would be robust because the government was investing "trillions" in infrastructure development and the country had remained attractive to foreign investors.

"The South African economy is moving forward and we are being recognised, by the way, by international institutions that we are doing very well.

"We were at Davos recently, that is what comes out, and the interest from investors to come to South Africa is very great."