This paper investigates the decision-making processes of mayors on the municipal level in Brandenburg, Germany, to support 100% renewable energy policies as well as the respective key success factors. Three different cases and their specific settings are examined: (1) Turnow-Preilack with Germany's largest solar power plant, (2) Prenzlau, a town claiming the title 'City of Renewable Energy’ and (3) the village of Feldheim, the first energy independent settlement in Germany. On the basis of exploratory site visits and interviews, the process of implementation of renewable energy is investigated. The methodology developed here is based on the 'theory of planned behaviour’ which helps to visualise the individual decision-making processes of key actors. Not surprisingly, many different factors influence the investigated cases. The decision-making processes must be investigated in their context that is shaped by the attitudes of mayors, the expectation of how their actions will be perceived, and the control mayors estimate to have over projects. The identified factors point at the key finding that the mayors first and foremost think about the 'good of their municipality’. This does not necessarily refer to economic factors but can encompass aspects such as 'strengthening community life’. More abstract factors such as climate change or contributing to the transition of the national power supply play - if at all - a minor role. Policies that aim at supporting energy transitions in similar settings should therefore shift their focus from communicating climate change mitigation to the co-benefits that ambitious renewable energy policies can bring to a community.