Burn, baby, burn

Although Eskom has significantly reduced its diesel usage over the last year, it is still much higher than it should have been if its power plants had performed well.

Last week, Eskom said load-shedding remained suspended despite the constrained power system due to maintenance and high electricity demand.

One way Eskom prevented load-shedding was to use open-cycle gas turbines (OCGTs) to produce additional electricity.

Open-cycle gas turbines are power stations that use diesel as fuel. They are intended for use during peak periods and emergencies.

They were never intended to run continuously for long periods and form part of Eskom’s base-load power generation.

However, Eskom has such severe operational challenges that it is forced to run OCGTs for extended periods.

Running OCGTs is costly. For example, Eskom has spent R3.4 billion on diesel over the past 30 days to prevent load-shedding.

“The OCGT load factor increased to 22.69% from 28 March to 3 April 2025, up from 20.83% recorded between 21 to 27 March 2025,” Eskom said.

This OCGT use is significantly higher than the 2.17% recorded during the same period in the previous financial year.

The power utility’s OCGT use peaked in the 2024 financial year, from 1 April 2023 to 31 March 2024, when it spent R33.35 billion on diesel.

Over the last financial year, from 1 April 2024 to 31 March 2025, Eskom cut its diesel expenditure by R16.51 billion to R16.84 billion.

Although this is commendable, it is still an order of magnitude higher than it should be if Eskom performed well.

For example, in 2017 and 2018, Eskom spent nearly no money on diesel. It used OCGTs as intended, which means its diesel costs were negligible.

This changed in 2019, with the return of load-shedding, and since then, diesel costs have rapidly increased.

Eskom’s diesel expenditure for the 2025 financial year is higher than in 2022, when OCGT use escalated rapidly.

The charts below show Eskom’s OCGT use and the money spent on diesel over the last decade.