Since 19 December (Eskom did not disclose breakdowns for the week prior), the level of unplanned breakdowns across its generating fleet has been above 12.5GW. On five of the 14 days disclosed — it skipped holidays — breakdowns were above 14GW.

Even with lower seasonal demand, it is almost certain that Eskom has been relying on emergency generation resources, including pumped storage schemes and open-cycle gas turbines (OCGTs), to keep the lights on over the holiday period.

While demand dropped significantly from 13 December as mines and factories shut down, the load has remained at around the 26GW level. Using 2018 published data, it is clear that load only drops below 25GW for the week between Christmas Day and New Year’s Day.

Necessary

Eskom said this step was necessary because it had to replenish water levels at its pumped storage schemes and diesel at its OCGTs overnight in preparation for the week ahead. On Sunday morning, however, Eskom said the “loss of additional generation units caused us to have to deplete our diesel and pump storage levels, which we need to restore as we head into the working week on Monday”. It has since repaired the conveyor belt failure at Medupi.

Usefully for Eskom, demand generally ramps up across the next two weeks as mines and factories reopen. Using last year’s data, it is clear that peak load only returns to “normal” summer levels of around 28GW by 15 January. This means it won’t suddenly face “normal” demand today (Monday, 6 January).

In addition, based on performance in December, non-commercial generation (the units at Kusile power station) has been able to add up to 900MW to capacity, which Eskom desperately needs.