The systematic planning of regional energy systems remains an issue of utmost importance for modern society. Thus, developing tools for effective design and communication with regional actors remains a relevant goal in research. This work presents an optimization-based decision workflow for regional energy planning aimed at enhancing stakeholder engagement and supporting informed decision-making during early design stages. Decision-making takes place within administrative units that exercise governmental functions through a top-down decentralization of responsibilities, often via federal structures. Within a given state, these units may include regions, counties, or political districts, as classified by the levels of the NUTS (Nomenclature of Territorial Units for Statistics) system. Consequently, within the decision-support process, stakeholders typically comprise the leaders of these administrative units, who possess substantive operational influence over the development of their respective entities. The proposed workflow integrates a rigorous optimization approach that permits the systematic generation of multiple solutions and the assessment of various scenarios for a given territory. The methodology is demonstrated through a case study in Carnica-Rosental, Austria, wherein four scenarios served as a platform for stakeholder dialogue and the development of integrated regional energy systems. The proposed workflow offers a powerful decision-support tool for systematic regional energy planning capable of providing insightful information about the region and serving as a platform for policymaking.