The building sector globally consumes 30% of primary energy, essentially from fossil origin. To foster an energy transition towards renewables, the adoption of renovation measures coupled with the penetration of distributed energy resources is crucial. In the Canton Valais, a centralized register for building data is lacking, hindering building energy performance simulation and distributed energy resource penetration scenarios for communes. This project aims to standardize cantonal data storage, visualize current and future built environments, and to evaluate and enhance distributed energy resource integration at the aggregated level. Leveraging existing open data, the project offers an open-access Geographic Information System (GIS) platform and Application Programming Interface (API) for scenario visualization. Additionally, an overview of Distributed Energy Resource (DER) penetration scenarios at the aggregated level is tested in three case studies. It provides a foundation for a cantonal platform, offering policy recommendation for stakeholders, especially energy utilities seeking to implement local storage solutions aiming at increasing the flexibility of the energy system.