29 October 2025

Koeberg Unit 1 Returns to Grid, Adding 930MW to Baseload Power

Eskom has successfully reconnected Unit 1 at Koeberg Nuclear Power Station to the national grid, restoring 930MW of generation capacity. The unit was synchronized at 01:36 on 29 October 2025, following its first scheduled major maintenance outage since the installation of new steam generators.

Both Koeberg Units Now Operational

With the return of Unit 1, both Koeberg nuclear units are now online and contributing to the national grid. Unit 2 is currently generating 941MW, while Unit 1 is in the process of ramping up to full capacity. Once completed, the combined output from Koeberg will exceed 1,860MW, representing approximately 5% of Eskom's total generation capacity.

Koeberg remains the largest nuclear generating facility on the African continent and provides critical baseload power to South Africa's electricity system.

Extended Operating License

The maintenance outage follows a significant milestone achieved in July 2024, when the National Nuclear Regulator (NNR) extended Eskom's license to operate Unit 1 until July 2044. This 20-year extension came after the successful completion of the Steam Generator Replacement Programme in November 2023.

Meanwhile, Unit 2 has been running continuously for 234 days at an impressive 99.88% year-to-date Energy Availability Factor (EAF). The unit is awaiting the NNR's decision on its own 20-year Long-Term Operation license, expected on 9 November 2025.

Comprehensive Maintenance Completed

The recent maintenance on Unit 1 included several critical activities:

• Comprehensive inspections and safety checks
• The statutory 10-year Integrated Leak Rate Test (ILRT)
• Fuel loading, which began in early September 2025
• Commissioning activities prior to synchronization

According to Eskom, the ILRT confirmed the containment building's structural integrity and leak-tightness, meeting international nuclear safety standards.

Bheki Nxumalo, Eskom's Group Executive for Generation, stated: "Our teams have demonstrated exceptional technical expertise and commitment. Koeberg remains a cornerstone of South Africa's energy mix, and this achievement underscores Eskom's continued focus on nuclear safety and operational excellence."

Maintenance Strategy

To maintain grid stability, Koeberg's maintenance outages are strategically staggered every 16 to 18 months. This approach ensures that both units are never offline simultaneously, maximizing the station's contribution to the national grid.

Outlook

The return of Koeberg Unit 1 strengthens South Africa's baseload generation capacity heading into the summer months. With both units now operational, Koeberg's contribution of over 1,860MW provides steady, reliable power that doesn't depend on weather conditions or time of day.

This development aligns with the recently released Integrated Resource Plan (IRP 2025), which continues to position nuclear power as part of South Africa's long-term energy strategy. The restoration of full capacity at Koeberg supports Eskom's efforts to maintain grid stability and adequate generation reserves.

However, while this represents positive progress for generation capacity, South Africa's overall Energy Availability Factor remains below target at 56.36%, suggesting continued challenges across the broader generation fleet.

Key Terms Explained

Baseload Power: Electricity that can be generated consistently 24 hours a day, providing the minimum level of demand on the electrical grid. Nuclear plants like Koeberg are ideal baseload providers as they can run continuously for long periods without interruption.

Energy Availability Factor (EAF): A percentage measuring how much of a power station's maximum generation capacity is available for use. A higher EAF indicates better performance. Koeberg Unit 2's 99.88% EAF is exceptionally high compared to Eskom's overall fleet average of 56.36%.

Integrated Leak Rate Test (ILRT): A comprehensive safety test performed every 10 years on nuclear containment buildings to verify their structural integrity and ability to prevent radioactive leakage. The test confirms the containment building can maintain pressure within acceptable limits.

Megawatt (MW): A unit of power equal to one million watts. For context, 1MW can power approximately 650-700 average South African homes. Koeberg's total capacity of 1,860MW could theoretically power over 1.2 million homes.