JOHANNESBURG: South Africa's struggling state utility Eskom said on Monday it aims to get its power plant performance to "acceptable levels" by late 2021, as scheduled outages entered a sixth day.

Eskom struggles to power Africa's most industrialised nation because of repeated faults at its ailing coal-fired power station fleet, constraining economic growth.

The utility said in a statement that it faced uncertainty of about 6,000 megawatts of capacity at any given time and that electricity supplies would remain volatile until a maintenance plan was completed by September.

It is focusing on correcting design defects at newer power stations, extending the life of older operating units, reducing unplanned outages and managing coal quality, it added in a presentation to reporters on the state of the power system.

"Eskom is committed to recovering its operational performance and will not compromise on ... maintenance and mid-life refurbishment," it said.