South Africa's energy woes are a "challenge" but not a crisis and 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 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 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."