In order for Greece to contribute its due share to the European energy and climate targets for 2030, as laid down by the Clean Energy Package texts and commitments, a true energy “renaissance” has to take place during the coming decade. This “renaissance” is urgently needed, in order to substantially upgrade and decarbonise an antiquated, highly inefficient and polluting national energy system, still relying heavily on domestic low-quality lignite and on imported oil. The scale of the required energy transformation that has to take place in the country, in the 2021-2030 period, if Greece is to meet its 2030 EU goals and international commitments is impressive: according to the Greek National Energy and Climate Plan (NECP, 2021-2030), investments totaling 35 billion euros have to materialise by 2030 in the Greek energy sector alone, two thirds of which will have to be channeled to energy efficiency, renewables and electricity transmission infrastructure/storage. The present paper explores key challenges posed on the Greek energy sector by the EU Energy Transition process and the application of the Clean Energy Package provisions and commitments, in the 2020-2030 period. In the crucial direction of securing the required green energy and the proper infrastructure needed for Greece’s energy transformation process, the paper discusses core energy issues, concerns and persisting obstacles that hinder or considerably slow down the required transformation (legislative, administrative, financial, etc.). Based on this analysis, the paper proposes specific policies, measures and top developmental priorities for the Greek energy sector in the coming decade, hopefully providing, as well, useful considerations for other South Eastern European countries.