Why Eskom’s improved performance still leaves SA exposed

In April 2024, the lights stayed on – after six years of load shedding this was headline news. Diesel generators and solar chargers were packed away, and most South Africans went back to life without hourly updates from the EskomSePush app.

But two years later, are things really as rosy as they look at Eskom?

Last week, Eskom provided us with the performance data for each of its power stations. This data is not publicly available, but Eskom provided the data to us in 2022 and ever since has kept up the tradition in the spirit of transparency.

The data shows each station’s energy availability factor (EAF) – the amount of time a station is ready and able to produce electricity – as well as planned maintenance (planned capacity loss factor, or PCLF) and breakdowns (unplanned capacity loss factor, or UCLF).

The picture is sobering: while the situation has improved, 40% of Eskom’s coal fleet still spent half of 2025 offline, either doing maintenance or – more often – fixing unexpected breakdowns.

62% energy availability factor

Eskom’s official target is an EAF of 80%. In 2025, it achieved a combined 62%, up from 59% in 2024 and 55% in 2023. Even though this falls far short of the (probably unrealistic) target of 80%, it is a borderline miracle.

However, bundling all Eskom’s different technologies into one number obscures the real picture. While coal still dominates its lineup, accounting for 84% of its installed capacity, it is not the only technology Eskom uses. Nuclear (e.g. Koeberg Nuclear Power Station) makes up 4%, pumped storage and hydro (e.g. Ingula Pumped Storage Scheme) makes up 7%, and gas – or rather diesel (e.g. Ankerlig Power Station) – makes up 6%.

What that data shows that is that most of these stations have much higher EAFs, which makes the picture look more pleasing. When one looks at coal in isolation, the EAF drops to a more sobering 58% in 2025.

But if Eskom’s coal-fired power plants were only available 58% of the time in the past year, what were they doing the rest of the time?

Breakdowns

Looking at EAF alone can be misleading: planned maintenance (which is good) eats into time available, but so do unplanned breakdowns (obviously bad). If one wants to get a clearer picture of how the coal fleet is performing, it’s better to focus on UCLF.

Here the picture becomes more alarming: in 2025, half of Eskom’s coal fleet spent more than 30% of their time offline for unplanned and unexpected repairs. Officially, the target is no more than 10%. Only Kusile, one of the new-build power stations that started operating in 2017, came close at 15%.

When Eskom first provided us with the station-by-station figures in 2022, the picture was worse. The coal fleet had an EAF of 53% (vs 58% in 2025), and breakdowns were eating up 35% of their time (vs 29% in 2025).

The series we published – The collapse of Old King Coal – tracked the deterioration of the coal fleet and examined how clinging to unrealistic EAF projects had led us into a load-shedding crisis that was not just predictable, but predicted by those with access to the data.

Read more: Part 1: The collapse of Old King Coal, Part 2: How unrealistic targets created an energy crisis, and Part 3: The war over the future of coal begins

The high level of breakdowns is a double blow: it increases the risk of load shedding but also makes the electricity Eskom does produce more expensive, as it tries to recoup the costs of the repairs off fewer megawatt hours.

To plug the gap left by the still recovering coal fleet, Eskom continues to burn diesel in open cycle gas turbines. Although diesel spend is a fraction of what it was in the 2022/23 financial year (R33-billion versus R5-billion year to date), it points to a system that is still under strain.

Recovery or retirement

The good news is that, according to the figures, things are improving. Between 2024 and 2025, most of the coal stations were moving in the right direction. A station like Tutuka, which was once considered irreversibly corrupt and broken, has almost doubled its EAF in the past year.

While Tutuka’s turnaround is astonishing, it still has a long way to go. Together with Arnot, Duvha, Grootvlei, Kendal and Kriel, these six stations – representing 40% of the coal fleet – have an EAF of 50% or less.

The worst performing station – Duvha, 20km from Emalahleni – had an EAF of 43%. This puts its EAF closer to wind power, which achieved an in capacity factor of 35%, according to data from the Eskom data portal. (Capacity factor is a slightly different measure to EAF, but it is the closest we have to comparing apples with apples.)

While the data confirms that Eskom has turned the EAF curve upwards, it also shows that the ageing coal fleet is not a silver bullet to prevent future load shedding.

Five power stations, representing 20% of the coal fleet, are scheduled to retire by 2030. Eskom has already assumed, in its medium-term outlook, that these stations will keep operating.

But keeping ageing stations online costs billions as critical parts become unsafe to use and need to be replaced. In 2019, a routine outage for a single unit at Tutuka was scheduled to cost R523-million, while replacing a switchgear that had become unsafe to use would cost R1.2-billion, all of which adds to the cost of the electricity Tutuka produces.

In the past, when Eskom had a monopoly, this wasn’t a problem – well-run stations merely subsidised the underachievers – but in an unbundled future, Eskom generation will be forced to compete on price.

In 2019, the government started to dismantle Eskom’s monopoly. By 2030, Eskom’s transmissions business will be in a standalone business, alongside the system operator, who conducts the symphony by deciding which power station to use to meet the country’s electricity demand.

Recently though, Eskom and the Department of Energy put forward a proposal that would claw back the transmission assets. The revised unbundling plan has caused an uproar from the private sector over concerns that Eskom generation (which owns the power stations) will use its position to stifle competition and force customers to keep buying electricity from under-performing coal-fired power stations.

Getting a clear-eyed picture of how each station is performing is step one in ensuring that South Africans get a fair deal, while also keeping the load shedding wolf at bay. DM

In the same spirit of transparency, we are publishing 11 years’ worth of station-by-station data that Eskom provided to us, covering the period from January 2015 to December 2025.