This paper introduces EneCross, a modular, scenario-based simulation platform designed to support the planning and evaluation of local energy communities (LECs). The platform integrates building, photovoltaic (PV), and battery energy storage models with optimization-based control strategies and is implemented as a web-based client–server architecture to ensure both technical accuracy and accessibility for non-programmers. The platform is demonstrated through real-world case studies at the BAM Campus, where results highlight three main findings: (i) scaling PV capacity strongly improves self-sufficiency but reduces self-consumption due to higher surplus generation; (ii) battery sizing offers benefits but with diminishing returns beyond certain capacity thresholds; and (iii) network topology critically influences flexibility and cost outcomes under peak constraints. By enabling rapid scenario configuration, execution, and visualization, EneCross provides a practical decision-support tool for stakeholders to explore cost-effective and sustainable LEC designs under realistic operational conditions.