An Athens court on Tuesday found several executives of the Energa and Hellas Power electricity companies guilty of stealing money from the state.
The court convicted Aris Floros and Nikos Dekolis of embezzlement.
Stefanos Siafakas, Achilleas Floros and Vassilis Milionis were deemed to be accessories to the theft.
Aris Floros was also convicted of smuggling, and, along with Siafakas and Dekolis, found guilty of money laundering.
Eight of the 19 suspects who stood trial were cleared.
The two companies withheld more than 100 million euros from the Greek state through a special property tax levied via electricity bills.
The companies allegedly collected the levies between September 2011 and November 2012 but subsequently failed to hand the money over to the state.
The defendants have offered to pay back 83 million euros but the court has yet to issue the necessary decision.