Siwko, the former CEO of state-run army equipment producer PGZ, will replace Daniel Obajtek, who resigned in February to become chief executive of Poland's biggest oil refiner PKN Orlen. Alicja Klimiuk has been Energa's acting CEO since then.

A string of recent changes in senior personnel at state-run companies -- some of which may be related to infighting within the governing Law and Justice (PiS) party -- have weighed on their valuations and the Warsaw Stock Exchange WIG20 <.WIG20>.

(Reporting by Agnieszka Barteczko; Editing by Catherine Evans)