Medupi Unit 4 Returns to Grid 8 Months Early, Adding 800MW to National Supply

2025-07-06

Eskom has successfully returned Medupi Power Station's Unit 4 to service, adding 800MW to the national grid — eight months ahead of the original repair schedule. The unit, which had been offline since August 2021 following a major explosion, resumed operations on Sunday evening.

Fast-Tracked Return Through Innovative Engineering

According to Eskom, the unit's early return was made possible through an innovative approach to repairs. Rather than waiting for a new Generator Stator to be manufactured — which would have significantly extended the outage — engineers sourced a refurbished stator from the Netherlands as an interim solution.

The Generator Stator, a critical component that converts mechanical energy into electrical energy, was severely damaged in the August 2021 explosion that took the unit offline. The refurbished replacement weighed approximately 400 tonnes and had to be transported nearly 1,000km by road from Richards Bay to the Lephalale power station.

All Six Units Now Operational

With Unit 4's return, all six units at Medupi are now operational for the first time since the 2021 incident. Once Unit 4 reaches full output in the coming weeks, the station will contribute a combined 4,800MW to the national grid — equivalent to roughly 10% of South Africa's total generation capacity.

Eskom Group Chief Executive Dan Marokane described the development as "a major milestone" in the utility's strategic objective to add 2,500MW to the grid through its Generation Operational Recovery Plan.

Contribution to Grid Stability

The return of Medupi Unit 4 represents another step in Eskom's efforts to maintain the suspension of loadshedding, which has been largely absent from South Africa since March 2024, with only occasional brief interruptions in early 2025.

"This achievement moves us closer to consistently overcoming loadshedding, which is now largely behind us due to structural improvements in the generation fleet," Marokane stated in the announcement.

While the additional 800MW strengthens the grid's capacity, it comes as Eskom's Energy Availability Factor (EAF) stands at 56.36%, still below the targeted 70% goal for winter 2025.

Outlook for Grid Stability

The return of Medupi Unit 4 provides a significant boost to South Africa's generation capacity and improves the grid's resilience. However, it's important to view this development within the broader context of Eskom's ongoing operational challenges.

While the generation fleet has shown improvements over the past year, the current EAF remains below optimal levels. The additional 800MW provides greater headroom during peak demand periods but doesn't eliminate vulnerability to clustered breakdowns like those that caused brief loadshedding episodes earlier this year.

With all six Medupi units now operational, attention will likely turn to maintaining their reliability and continuing the implementation of Eskom's Recovery Plan, which aims to further stabilize the grid through increased maintenance and operational improvements.

Medupi's Environmental and Social Impact

Medupi Power Station, one of the world's largest dry-cooled coal plants, incorporates supercritical technology that allows for higher operating temperatures. This improves efficiency while reducing coal and water consumption — an important consideration given the water scarcity in Lephalale.

The station is designed to recycle process water and features low nitrogen oxide burners to reduce emissions. Eskom notes that the plant has been designed to accommodate future flue gas desulphurisation technology, which would reduce sulphur dioxide emissions by more than 90%.

Beyond power generation, Eskom reports that Medupi has contributed to regional development through over R2.9 billion in socio-economic initiatives during construction and R145 million in corporate social investment programs benefiting approximately 80,000 people.

Key Terms Explained

Energy Availability Factor (EAF): A percentage measuring how much of Eskom's total generation capacity is available for use. Currently at 56.36%, it represents the portion of Eskom's fleet that can produce electricity at any given time. A higher percentage means more reliable power supply.

Generator Stator: The stationary part of a generator that contains coils of wire. When the rotor (spinning part) turns inside it, electricity is produced. It's essentially the heart of any power generation unit.

Supercritical Technology: An advanced coal power generation method that operates at higher temperatures and pressures than conventional plants. This results in better efficiency (more electricity from the same amount of coal) and lower emissions.

Megawatt (MW): A unit of power equal to one million watts. For context, 800MW (Medupi Unit 4's capacity) can power approximately 520,000 average South African homes.

Flue Gas Desulphurisation: Technology that removes sulphur dioxide from exhaust gases produced when burning coal, significantly reducing air pollution and acid rain potential.