The role of the city in environmental management is increasingly coming to the fore. A central element in creating urban environmental sustainability is the adoption of appropriate energy policies, since most environmental externalities in cities are directly or indirectly related to energy use. The current practice demonstrates an overwhelming variety of initiatives and policies, so that the actual success of such strategies in a cross-sectional comparative perspective is hard to evaluate. In this context, this paper offers an application of meta-analysis, as this approach is an interesting analytical contribution towards a better understanding of the critical success factors of urban energy policies. The paper starts with a general overview of the issue of urban sustainability and sets out the importance of energy policies at the urban level. It continues by offering a methodological framework for the assessment of critical factors related to the performance of sustainable energy strategies. Using a database containing information on experiences and expert expectations reegarding renewable energy initiatives in 12 European cities spread over 3 countries (Italy, the Netherlands and Greece), we offer a cross-European comparative analysis of the performance of urban renewable energy technologies. This comparative data and the application of a specific meta-analytical method, called rough set analysis. The paper ends with a concluding section on policy lessons.