LIGHTNESS will increase the Renewable Energy hosting capacity, to securely achieve the EU target for 2030, by supporting the market uptake of Citizen Energy Communities through a turnkey social engagement, regulatory roadmap, low-cost technological package and innovative business models to unlock the full flexibility potential, reduce the final energy consumption and CO2 emissions and bring economic, social and environmental benefits to the communities and across the energy value chain. LIGHTNESS solution will elaborate and execute ambitious end users engagement plans for the involved sites with continuous iterations and solution adaptation to achieve a direct engagement of +500 households and +30 tertiary buildings and an immediate replication potential to over 70.000 persons. LIGHTNESS solution will create digital twins for holistic assessment of 5 CECs case studies across 5 countries to be then deployed and monitored. Case studies consist of an energy cooperative (ES), a social housing building (PL), a private multi-apartment building (IT), a business park (FR) and 2 CECs to uphold the interaction among them (NL). The different regulatory and policy frameworks will allow to exchange best practices and providing road maps for the authorities.