In every country, the energy sector plays a very important role - from its efficient operation electricity and heat supplies depend on. Moreover, its level of efficiency can measurably affect the condition of the natural and the social environment. Therefore, the purpose of this article was to examine to what extent the Polish energy sector fulfills the framework of sustainable development conception. In order to achieve the adopted objective, comparative analyzes have been carried out among all European Union countries. It allowed to identify areas in which the Polish energy sector fully implements the principles and objectives of this concept, as well as areas where still there is a lot need to be dome. The analyzes concerned several key issues: the level of energy generated from renewable energy sources (RES), the structure of sources of raw materials for energy production, the values of regulatory indicators for sustainable energy, level of greenhouse gas and pollutants emissions by energy sector, environmental taxes paid by energy sector, environmental protection expenditure of energy sector, environmental investments and wastewater management and, last but not least, innovations expenditures of energy sector. Examining these issues makes it possible to determine the so-called “level of sustainability" or the sustainability in energy sector degree’s determination for Poland.