A concise set of energy indicators is proposed to assess the sustainability of the Greek energy system from 1960 onwards. Three generalized indices, each corresponding to one of the three dimensions of sustainable development (social, environmental and economic) are defined, estimated and presented in the form of a ternary plot. Results are used to analyze whether the energy system developed in a sustainable way, and to identify its weaknesses and deficiencies. The analysis further demonstrates the representativeness of the chosen set of indicators, and its ability to describe the most significant changes that occurred during the studied period.The analysis spans a period of 47. years, during which significant political, social and economic events took place in Greece. Results show that the development of the energy system has been mainly driven by social aspects. Environmental performance improvements are particularly evident during the last decade; however, a lot remains to be done to achieve national and European policy objectives. With regard to the social dimension, accessibility has substantially improved and disparities between low and high income households have narrowed. Nevertheless, energy prices have been continuously increasing at a rate higher than income. On economic terms, the initially observed improvement in productivity is misleading, as it was mostly caused by the increase of the Gross Domestic Product rather than energy efficiency improvements, while energy security has been worsening during the last decade.