- The Energy Availability Factor rose sharply in December, supporting grid stability and reduced diesel use.
- Eskom says data must be viewed in context of long term maintenance and reliability gains.
- Eskom has reaffirmed the stability of South Africa’s power system following questions raised about the sharp improvement in its Energy Availability Factor during December.
According to Eskom, the Energy Availability Factor reached 69.14 percent in December 2025, representing a year on year improvement of 12.57 percentage points compared to 56.57 percent in December 2024. On a year to date basis, the indicator increased to 64.35 percent, with the generation fleet meeting or exceeding the 70 percent benchmark on 49 occasions.
The improvement has largely been driven by a reduction in unplanned outages, reflecting better maintenance execution and the successful return of long outage generation units. However, energy analyst Chris Yelland has publicly questioned the unusually high Energy Availability Factor reported in the final weeks of 2025, suggesting the figures appear inconsistent with historical trends.
In a post on X, Yelland said the data point for week 52 of 2025 was so atypical that it raised concerns about whether operational activities had been adjusted to present a high year end figure. Official Eskom data portal reports show the Energy Availability Factor of 66.12 percent as at 19 December, with a final monthly average of 69.1 percent.
Eskom responded by explaining that the Energy Availability Factor measures the percentage of the generation fleet available to supply electricity after accounting for planned maintenance, unplanned breakdowns and other constraints such as coal quality. The utility said improved reliability across the fleet allowed it to reduce planned maintenance during the festive season without compromising overall system stability.
The decision to scale back maintenance in December was aligned with the Generation Recovery Plan and supported by lower electricity demand during the holiday period. Eskom confirmed that the annual planned maintenance benchmark of 10 percent will be maintained going forward.
This year’s operational performance allowed Eskom to spread maintenance more evenly across the calendar year, following what it described as intensive and necessary maintenance in 2023 and 2024. The utility said this short term pressure strengthened the structural integrity of the generation fleet and delivered the reliability gains seen in 2025.
High plant reliability and lower seasonal demand also enabled Eskom to place up to 13 675 megawatts of capacity into cold reserve, primarily from coal fired power stations. Eskom said this level of excess capacity was not possible in previous years and helped reduce wear on equipment and operating costs.
The improved performance contributed to a reported saving of R2.5 billion in diesel costs compared to the previous year, with no diesel expenditure recorded over the final two weeks of December.
Eskom said any assessment of its production data should be grounded in evidence and considered within the context of its broader strategy, long term performance trends and validated operational outcomes.
Author: Bryan Groenendaal
