Positive energy districts (PEDs) are gaining momentum as solutions to decarbonize urban environments. Nevertheless, they represent complex techno-socio-economic systems that integrate a variety of stakeholders and technologies, and the necessary conditions for their adoption remain unclear. To facilitate the wide rollout of PEDs, the Pol4PED project aims to design targeted policy mixes, tailored to diverse European urban contexts, with a focus on existing urban districts and regeneration. We will develop a toolbox, employing a platform-based design (PBD) approach to integrate different techno- and socio-economic models that reflect the interplay of different PED aspects. This methodology ensures that policy designs are informed by a comprehensive understanding of PED dynamics, addressing technical feasibility, economic viability, legal structures, and social acceptance under different political boundary conditions. The project involves case studies in Zurich (Switzerland), Vienna (Austria), and Groningen (the Netherlands), allowing for exploration of local contexts in policy decision-making for PEDs. By identifying best practices and formulating comprehensive policy insights, our project aims to accelerate sustainable urban energy transitions. Pol4PED offers a pioneering solution to the challenges of urban energy transformations through its innovative, multi-domain approach, and demonstrates the critical role of policy in achieving sustainable urban development.