In response to climate change, the limited availability of fossil fuels and the risks associated with nuclear energy, Germany’s energy transition aims to achieve a sustainable, environmentally sound supply of energy services. A monitoring process was established by the Federal Government to ensure that the targets defined for the transformation will be reached. The indicator system developed for that purpose mainly focuses on “classical” environmental, economic and technological indicators for which statistical time series data and political targets are available. Important socio-technical aspects of the energy system and its transition, such as affordability, participation and acceptance, remain largely neglected. This paper aims to contribute to the discussion on indicators needed for political decision-making to appropriately address sustainability aspects of the energy system and its transition, as well as to contribute to improving existing indicator systems. Therefore, the sustainability rules of the Integrative Concept of Sustainable Development were translated into indicators based on an in-depth literature review. The resulting abundance of possible indicators was then reduced using selection criteria such as comprehensiveness, possibility to determine targets and availability of data. ... mehrFinally, the indicator system was adjusted based on feedback of experts from different disciplines and stakeholder interviews in the particular investigation area of southwest Thuringia. Besides classical indicators related to techno-economic and environmental aspects, the finally developed indicator system includes new sustainability indicators related to the socio-technical interface of the energy system. Thus, it is considered suitable for assessing the sustainability of the Germany energy system and its transition in an integrative and comprehensive way. The indicator system is helpful to systematically identify strengths and weaknesses of the energy system and interdependencies and conflicts of goals between different sustainability aspects. All in all, we believe that applying the indicator system appropriately can support the development of resilient political strategies for a successful energy transition.