Do mitigation plans come true?

European cities voluntarily adopt targets and climate action plans with the objective of reducing GHG emissions related to urban activities. Although studies confirm the importance of cities’ action in mitigating climate change, it is still unknown the extent to which their mitigation plans become a reality, and the factors that influence their execution. This study is one of the first attempts to assess the status of implementation of urban-scale mitigations actions undertaken by 113 European cities through the Sustainable Energy Action Plan, and to analyse the governance factors that drive and constrain the implementation of such measures. The governance factors are related to the three variables: local framing, political actors and factors, and local government capacity, which institutionalises the governance aspects within local governments. Based on a survey, SEAPs’ monitoring reports, and academic literature, the study shows that 58% of the mitigation actions are being implemented, while the other half is divided into completed and not started actions. Political authority and the inclusion of the mitigation policies in the city’s budget appear as the main drivers of implementation, while the main barriers are lack of staff and the fact that climate change mitigation is not mainstreamed among other government’s departments. The availability of knowledge and information regarding mitigation at the local level is both considered as a main driver and a main barrier. The study also analyses the critical factors of implementation in each of the nine sectors of the SEAP. In two-thirds of the sectors, it is essential that the mitigation actions are aligned with the cities’ priorities and with national policies, while the most common barriers to implementation across sectors are the resistance of the private sector and the lack of cobenefits offered by the measures adopted. Furthermore, the analysis highlights that the mitigation actions related to local electricity production have the highest potential to reduce emissions, but are the least implemented by European cities, mainly because of the interactions of the local governments with the national government and the private sector.