Eskom announces weekend rolling blackouts to replenish emergency diesel reserves as units go offline

7 Mar 2025

Stage 3 load shedding is back for another weekend, but Eskom promises that it’s temporary

Eskom has announced that South Africans will be subjected to Stage 3 rolling blackouts this weekend. However, the utility said the country “is in no way returning to the levels of load shedding that we experienced in 2023”.

In a statement on Friday afternoon, 7 March, the utility said the decision to implement rolling blackouts follows the loss of 2,700MW in the past 14 hours.

“This includes Koeberg Unit 2, which was taken offline after being brought back on Wednesday, and two Kusile units whose coal operations went sub-optimal following adverse weather in the area.”

Eskom explained that the loss of this capacity occurred while higher levels of planned maintenance outages “aimed at winter preparation and meeting regulatory and environmental licensing requirements are still under way”.

“The constrained capacity resulted in the increased reliance on emergency reserves during this week, which makes it necessary to focus on replenishing these critical resources during the weekend in preparation for the business week,” the statement continued.

Clyde Mallinson, an independent energy analyst, told Daily Maverick that the above is “code speak” for Eskom’s having been burning diesel all week and now needing to refill the pumped storage over the weekend. Not having this pumped storage capacity available, in addition to the loss of Koeberg Unit 2 and the units at Kusile, would have almost inevitably led to rolling blackouts.

What got us here?

Chris Yelland, MD of EE Business Intelligence, shared more information about the confluence of factors that led to this most recent bout of rolling blackouts.

On Sunday, 1 March, Eskom announced: “Unit 2 of the Koeberg Nuclear Power Station experienced an unplanned, non-technical trip while operating at full capacity.” On Wednesday, it was brought back online and then taken offline during this most recent incident.

“When both units at Koeberg are off, the risk of a system instability increases very significantly because a lot of power is now coming from the north to the south of South Africa. If one of the lines from the north trips out now, there will be a regional blackout in the Western Cape,” Yelland told Daily Maverick.

Traditional power generation relies on large rotating machines – synchronous generators – that provide system stability through their rotating mass, which helps maintain voltage and frequency. To maintain stability, Eskom has had to rely more on the Ankerlig open-cycle gas turbines (OCGTs), among others, in the Western Cape, which, while expensive, provide both immediate power and some stabilising inertia that the system requires in Koeberg’s absence.

“And when you run the open cycle gas turbines hard for a week, you run out of diesel because their storage facilities are quite limited,” Yelland said.

With Koeberg offline and the emergency reserves in the form of OCGT’s and pumped storage needing to recuperate their reserves, the “system is running very tight”.

And then you get to the “adverse weather” – likely in the form of wet coal – shutting down two units at Kusile. The result is a situation where there is almost no alternative to load shedding.

Yelland, careful not to definitively say this is what happened, explained that “wet coal becomes a problem when your coal stockpiles are not full. If you're running the coal stockpiles close to empty or half full or quarter full, then towards the bottom of the stockpile is a whole lot of coal fine.

“It’s like powder. It’s crushed coal. When that gets wet, it turns into like mud, like a slush, and it causes problems on the conveyors and cause blockages of the coal chutes.”

Eskom explains

In recent weeks since Eskom broke its more than 300-day streak of no rolling blackouts, Minister of Energy and Electricity Dr Kgosientsho Ramokgopa and Eskom’s executive team have been at pains to explain that the system has been running with low reserve margins because of the depth and extent of the maintenance being undertaken on the coal fleet.

This has meant that should there be some unanticipated loss of capacity, the options for Eskom to respond without resorting to rolling blackouts are greatly diminished.

In a briefing to Parliament’s Standing Committee on Public Accounts (Scopa) last week, Eskom Group chief executive Dan Marokane said that when Eskom finishes this “cycle of deep maintenance” and from the end of March, when many of these units begin coming back online, Eskom would get back to “a comfort level that helped us manage the long period of no load shedding”.

Read more: Parliament told Eskom needs two things before ‘ultimate certainty’ load shedding is over

Eskom’s statement on Friday said that in the short term, the utility is “deploying extra engineering resources to expedite the repair of units currently offline. It is anticipated that 6,200MW will be restored to service by Monday’s evening peak.”

“We reiterate our commitment to ensuring that South Africa is in no way returning to the levels of load shedding that we experienced in 2023. Two years into delivering the generation recovery plan that will bring an end load shedding, we are at a challenging time and the full force of our highly skilled engineering resources are deployed and focused,” said Eskom’s head of generation, Bheki Nxumalo.

“We have had some delays in returning units that previously tripped back to the grid, as well as to the return of three units that have been on longer-term outage that will bring back 2,500MW to the grid, which will happen over the coming weeks,” Nxumalo said. DM

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What got us here?

Eskom explains