Renewable Energy Communities (RECs) are gaining momentum across Europe as an effective instrument to accelerate the decarbonisation of buildings, foster local energy sharing, and engage citizens in the clean energy transition. However, practitioners, researchers, and public bodies often struggle to access transparent and replicable methods to design, simulate, and assess the performance of these configurations.

Two complementary open-source tools, developed through Italian and European research collaborations, are now available to help fill this gap.

The CACER Simulator, developed by RSE (Ricerca sul Sistema Energetico) and co-developed with Eurac Research and other Italian organisations, is a modular Python-based simulation platform for Configurazioni di Autoconsumo per la Condivisione dell'Energia Rinnovabile (CACER) — the Italian regulatory framework for RECs. The tool combines an energy flow model, a financial model incorporating the incentive mechanisms of ARERA Deliberation 727/2022, and a load flow model for grid impact assessment. Targeted at researchers, public bodies, PhD students, and technically proficient users, the CACER Simulator is freely available on GitHub and evolves through a community of developers and researchers committed to open-science principles.

pyBuildingEnergy, developed at Eurac Research's Institute for Renewable Energy within the MODERATE Horizon Europe project, is an open-source Python library implementing the ISO 52016-1 standard for dynamic building energy simulation. It provides a standardised and reproducible computational layer for building-level energy performance assessment across different building archetypes and climatic contexts.

Used together, these tools make it possible to connect building-level physics with community-scale energy sharing dynamics. This supports evidence-based planning of RECs in residential, commercial, and public sector settings.