This is according to South African power utility Eskom responding to a report in the Business Day newspaper.
"It would not be correct to say categorically that it would take five years. That is a worst-case scenario," Eskom spokesman Andrew Etzinger told Reuters.
Etzinger was responding to a report in the Business Day newspaper that said the poor state of the country's power stations would keep supply margins razor-thin for at least another five years. It cited a presentation it said was prepared by Eskom management.
(READ MORE: Eskom facing liquidity crisis as privatisation looms)
Eskom, which supplies virtually all of the power for Africa's most advanced economy, is scrambling to keep the lights on by building new stations while trying to maintain and repair older ones.
The Medupi power station under construction is supposed to be feeding 800 megawatts (MW) to the grid by the middle of 2015 and will eventually provide 4,800 MW. A second station, Kusile, is scheduled to start supplying power a few months later.
Both projects have been plagued by delays which have included flare-ups of violent labour unrest.
(READ MORE: Eskom says power system under pressure)
"Medupi coming on line will not be an instant power resolution. This has been our position for some time," Etzinger said.
"But with the combination of Medupi and Kusile we will see a steady improvement of the situation," Etzinger said.
The two stations will eventually provide 9,600 MW, about a quarter of Eskom's current capacity which is usually close to 35,000 MW.
In March Eskom was forced to impose rolling blackouts for the first time in six years to prevent the national grid from collapsing, a situation that underscored just how precarious the balance is between power supply and demand.
Power constraints are frequently cited as a key reason behind sluggish growth in South Africa, where the economy narrowly missed a recession in the second quarter when it expanded by a tepid 0.6 per cent.