Many towns and cities worldwide have begun implementing decentralised urban energy systems. Aiming to reduce their carbon emissions, many utilise not only technological innovation but also innovative policy and financial and social–economic approaches. Following interviews with stakeholders, four international cases, all of which were defined by stakeholders in different ways as “successful”, provide insights into the instigating driving forces contributing to success. Understanding of “success” varied between projects and between stakeholders, depending significantly on individual attitudes to sustainability, financial feasibility, technical performance and social acceptance, suggesting that a realistic definition of success involves not just a project's financial feasibility and energy savings, but that enhancing high-potential partnerships and transparency, and acceptance and understanding of the proposed project are also critical, as are interest from the media and outside organisations. The success of a project therefore cannot be measured simply via its outcomes – process factors and the context in which they unfold are also crucial.