The development of the energy sector and the awareness on its effects onto the environment, have generated ample concerns on the protection of the environment against emissions that are produced along all phases, namely the extraction of energy carriers, the conversion thereof into electricity or another form of energy, the transportation and distribution of energy, and also along the processes being carried out at the level of the end user. The studies conducted on the sustainable development of the energy sector revealed the need that an analysis be performed not only in regard to the effects onto the environment, but also in regard to the effects onto the social and economic components. The World Energy Council performed an in-depth analysis of the issues underpinning the future of the energy sector and developed the concept of „energy trilemma”, as a concept where the energy security, the environmental protection and the access to modern energy are vital elements to be considered when assessing the sustainability of the energy sector. The paper examines the factors that exert an influence onto the sustainable development of the sector, the concerns on mitigating all forms of environmental pollution, but also the provision of users with access to energy, at affordable prices. The ecological footprint of the sector, alongside the determination of the quantity of avoided CO2, are important criteria in the assessment of efforts required to ensure the sustainability of the energy sector. The paper also examines the current solutions that provide for a sustainable development of the energy sector.