During his testimony last month, Koko, told the commission that there was an orchestrated witch-hunt against him because he preferred nuclear power over renewable energy.
He said the two energy plans represented two different political interests: President Cyril Ramaphosa, who pushed for renewable energy, and former president Jacob Zuma, who preferred nuclear power.
Previously, Koko alleged that Ramaphosa had interfered in his dismissal in 2018.
This week the commission is also expected to hear evidence from the parastatal's ex-CEO Brian Molefe, and former CFO Anoj Singh.
TimesLIVE