Here’s the data showing how Eskom is able to keep SA’s lights on

Eskom data show that a drop in demand and repairs to Kusile largely explain why we’ve had no load shedding for over 200 days, but some coal-fired power plants remain a problem.

At 5am on Tuesday, 26 March, load shedding came to an abrupt end. Since then, South Africa has enjoyed over 200 days without load shedding, including our first winter in five years where the lights stayed on.

amaBhungane Centre for Investigative Journalism took a deep dive into Eskom’s data to find out why.

The simple answer is: demand is down and the performance of the coal fleet is up. But a closer look at the individual stations reveals a more complex picture.

Demand is down, coal is up

Between 2023 and 2024, the demand for electricity dropped by, on average, 804MW an hour. That may not sound like much – Eskom has an installed fleet of 46,686MW – but it’s almost one stage of load shedding.

We looked at the “RSA contracted demand” from September 2023 to August 2024 and compared that with the previous year – in simple terms, this is the amount of electricity Eskom needs to meet the country’s demand at any given time.

The average hourly demand has dropped from 25,908MW in the 2022/23 period to 25,105MW in 2023/24. The drop in demand is particularly noticeable in the middle of the day, which suggests that rooftop solar at residential homes is having a real impact.

At the same time, the coal fleet has been performing better by, on average, 1,012MW an hour.

The data shows an increase in average “thermal generation” – electricity derived from burning coal – from an average of 18,714MW an hour in 2022/23 to 19,725MW in 2023/24.

As these two lines move closer together – demand coming down and coal going up – the gap that needs to be filled by nuclear, renewables, hydro, diesel or with load shedding gets more manageable.?

And over the past year, the gap has narrowed by, on average, almost two stages of load shedding.

• Eskom publishes graphs showing how demand is met on a day-to-day basis through the Eskom data portal. In the past week, for instance, we’ve relied heavily on wind, imported electricity from our neighbours and burning diesel.

What about diesel?

A question many people have is, are we blowing Eskom’s budget on diesel just to keep the lights on?

We looked at the data for the Open Cycle Gas Turbines (OCGTs), specifically the period from April 2024 when load shedding stopped. Between 1 April and 31 August 2024, the OCGTs – those owned by Eskom and by Independent Power Producers – generated 510GWh of electricity.

That’s not nothing, but it’s a lot less than the same period in 2023, when the OCGTs produced 2,359GWh of electricity. In other words, we used four times more diesel over winter in 2023 than we did this year.

But despite using less diesel – which normally keeps the load shedding wolf at bay – the data also shows that “manual load reduction” (aka load shedding) dropped as well: from 7,212GWh between April to August 2023, to zero this year.

But the picture is not entirely rosy across the board.

The coalface

A deeper dive into Eskom’s data indicates that while some coal-fired stations are improving, others are facing challenges.

The Energy Availability Factor (EAF) of an Eskom plant is the amount of time a power plant is available to produce electricity – expressed as a percentage – after planned maintenance (PCLF), breakdowns (UCLF) and other causes (OCLF) have been taken into account. (Strictly speaking, it’s not how much electricity a power station actually produces, but this is how Eskom prefers to display its data.)?

Our analysis of the data shows that the EAF of the coal fleet has improved, particularly over the five months from 1 April to 31 August 2024, from 51% in 2023 to 60% in 2024. This is particularly impressive considering that Eskom also spent marginally more time doing maintenance this winter (+2%) when compared with 2023.

Several coal-fired stations – Kusile, Hendrina, Grootvlei, Matla, Kendal, Majuba, Tutuka, Kriel and Matimba – have improved their EAF in 2024, while others – Arnot, Lethabo, Camden, Medupi and Duvha – have gone the other way.

Read the full analysis on Daily Maverick, authored by Buyeleni Sibanyoni and Susan Comrie for amaBhungane Centre for Investigative Journalism

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