Power System Stable Despite Slight EAF Decline as Winter Approaches

2025-05-09

Power System Remains Stable as South Africa Heads into Winter

South Africa's power system continues to show stability heading into the winter months, with unplanned outages currently at 11,670MW, down from 12,644MW recorded last week. This stability comes despite a slight decline in the Energy Availability Factor (EAF) compared to the same period last year.

According to Eskom's latest operational update, the country's available generation capacity currently stands at 29,167MW (excluding 720MW from Kusile Unit 6), with tonight's peak demand projected at 27,428MW.

Unplanned Outages Show Improvement

The Unplanned Capacity Loss Factor (UCLF), which measures unexpected breakdowns in the generation fleet, currently stands at 27.99% for the financial year-to-date (April 1 to May 8, 2025). This represents an improvement of approximately 1.2% compared to the 29.15% recorded during the same period last year.

From May 2 to May 8, 2025, unplanned outages averaged 12,273MW, showing a marginal increase of 112MW compared to the same period last year. Since April 1, the average unplanned outages stand at 13,089MW.

Planned Maintenance Increases

Eskom has increased its planned maintenance activities, with an average of 6,904MW (equivalent to 14.76% of total generation capacity) under maintenance since April 1. This reflects a 3.32% increase compared to the same period last year.

The higher maintenance levels are partly responsible for the slight decline in the overall Energy Availability Factor (EAF), which stands at 56.77% year-to-date, down from 58.97% during the same period last year.

Winter Outlook: Limited or No Loadshedding Expected

Eskom presented its Winter Outlook on May 5, 2025, covering the period until August 31, 2025. According to this outlook, loadshedding is not anticipated if unplanned outages remain below 13,000MW.

Should outages increase to 15,000MW, loadshedding would be limited to a maximum of 21 days out of 153 days at Stage 2. This represents a significant improvement over last winter's worst-case scenario, which predicted Stage 5 loadshedding.

To further stabilize the grid, an additional 2,970MW of generation capacity is expected to return to service before the evening peak on Monday, May 12, 2025.

Diesel Usage and OCGT Utilization

The Open-Cycle Gas Turbine (OCGT) load factor stands at 3.87% during the past week (May 2 to May 8, 2025), marginally up from 3.78% recorded in the previous week.

Year-to-date, Eskom has spent approximately R2.43 billion on fuel for the OCGT fleet, generating 415.91GWh. This is higher than the 175.20GWh generated during the same period last year. However, the OCGT load factor for the year-to-date stands at 13.36%, representing a 13.8% decrease from the previous week.

Eskom expects diesel usage to decline as maintenance activities wind down and additional units return from long-term repairs during the winter months.

Warning Against Illegal Connections

With electricity demand rising during winter, Eskom has urged the public to help prevent transformer overloads and related equipment failures by avoiding illegal connections and purchasing electricity only from accredited vendors.

Eligible households are encouraged to register for free basic electricity with their local municipalities, and the public is reminded to report any illegal activities impacting Eskom's infrastructure.

Outlook

As South Africa moves deeper into winter, the power system appears to be in a better position than in previous years. The reduction in unplanned outages to below 12,000MW provides some buffer against winter demand peaks, though the system remains constrained.

The slight decrease in the Energy Availability Factor, primarily due to increased planned maintenance, suggests Eskom is prioritizing long-term reliability over short-term availability. This strategy, if successful, could lead to improved performance as these units return to service.

However, the continued high level of diesel generation compared to last year indicates that emergency reserves are still playing a significant role in grid stability, despite the overall improvements.

Key Terms Explained

Unplanned Capacity Loss Factor (UCLF): The percentage of Eskom's generation capacity that is unavailable due to unexpected breakdowns. Lower UCLF indicates fewer breakdowns and a more reliable system.

Energy Availability Factor (EAF): The percentage of Eskom's total generation capacity that is available for use. An EAF of 56.77% means just over half of Eskom's theoretical maximum generation capacity is actually available to produce electricity.

Open-Cycle Gas Turbines (OCGTs): Emergency power generators that run on diesel. They're expensive to operate (about R4.50 per kWh vs. R1.40 for coal) but can be started quickly when needed. They're similar to jet engines connected to generators.

MW (Megawatt): A unit of power. 1MW can power approximately 650 average South African homes. Eskom's total installed capacity is around 46,000MW.

GWh (Gigawatt-hour): A unit of energy. 1GWh is enough electricity to power about 650,000 homes for one hour.