Koko and the other accused appeared in a magistrate's court and applied for bail, footage from the SABC showed.
An NPA statement said the charges related to allegedly irregular contracts valued at more than R2bn in the building of Kusile, which has been riddled with faults and costs far more than was originally intended.
Koko did not immediately respond to Reuters seeking comment.
However, in a clip posted on Twitter by broadcaster eNCA, Koko said his accusers had "set themselves (up) for failure".
Koko resigned from Eskom in 2018 after being accused of violating procurement rules but was acquitted in a disciplinary hearing.
In his resignation letter, he did not admit wrongdoing.
A spokesperson for the National Prosecuting Authority (NPA) said the accused were not expected to enter a plea at this stage.
South African prosecutors have been trying to make headway with a string of corruption cases dating back to former President Jacob Zuma's era. Zuma has denied all corruption allegations levelled against him.
In May, police arrested several former executives of another big state company, Transnet, for alleged corruption.
Swamped in billions of rands of debt, Eskom has been mired in financial crisis for years. This year it implemented a record amount of load shedding, fuelling public anger and choking economic growth.
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