South Africa's struggling state-owned utility Eskom said on Wednesday that the power outlook remained highly uncertain, with unplanned outages often varying by 2,000 megawatts (MW) in one week.
Repeated breakdowns at Eskom's coal fleet are a major brake on economic growth in Africa's most industrialised nation.
The company with a nominal capacity of around 46,000 MW has implemented scheduled power cuts on more than 30 days so far this year, more than in the same period last year when power cuts reached record levels.
At a news conference, Eskom said in its base case of 12,000 MW of unplanned outages over the April-August winter months no days of scheduled power cuts were seen.
But in a scenario with 13,500 MW of unplanned outages there could be 37 days of power cuts during winter and 104 days in a scenario with 15,000 MW of unplanned outages.
More than 15,000 MW of capacity was offline because of breakdowns at various stages this week.
Eskom will implement "Stage 2" power cuts from 1700 to 2200 local time (1500 GMT to 2000 GMT) on Wednesday after three generation units failed, requiring up to 2,000 MW to be shed from the national grid.
Eskom generates more than 90% of South Africa's power but has struggled to meet demand for more than a decade. President Cyril Ramaphosa's government has promised to make the firm more efficient, but progress has been difficult.
Eskom said on Wednesday that none of its 15 coal stations were operating at full capacity.
(Reporting by Alexander Winning in Johannesburg and Bhargav Acharya in Bengaluru, Editing by Louise Heavens)