Prospective environmental impact of solar energy communities in a decarbonised grid: insights from consequential life cycle analysis

Energy communities (ECs) are increasingly recognised as a key instrument of the energy transition due to their potential to deploy decentralised renewable energy, reduce emissions, and empower citizens. However, their modelled outputs are often simplified to their operational lifetime and the current technology context, thereby failing to capture their long-term sustainability and true ex-ante emissions. This work evaluates the prospective environmental impacts of solar energy communities using Life Cycle Assessment. Two EC technology configurations are assessed: PV and PV plus a battery (BESS). Considering the greenhouse gas (GHG) emissions from cradle-to-gate , and the future electricity grid mix anticipated under decarbonization pathways, the GHG emissions reduction and optimal PV sizing for the 2019, 2030 and 2050 horizons are studied for a case study in Lisbon, Portugal. It is concluded that for the best EC configuration (PV + BESS), emission savings decrease considerably as the grid mix becomes greener. Savings reach 88% in 2030 but fall to 15% in 2050. Results indicate a temporal decline in optimal PV sizing. In 2019, all scenarios converge on PV installation across 100% of the available EC rooftop area, whereas optimal coverage decreases to 30% and 20% in 2019 and 2050, respectively. These findings suggest that the long-term value of ECs depends not only on their local deployment but also on timely integration with evolving energy systems and policy frameworks. Altogether, this reveals that as their climate mitigation gains diminish in a decarbonised grid, the long-term relevance of EC increasingly lies in their socioeconomic and system-level benefits.