The present study documents the methodology and results of modelling in order to quantify the benefits of electricity and gas related Projects of Common Interest (PCIs) for the European Power and Gas systems. The quantitative scenario analysis was conducted using the METIS model and quantified the potential benefits of already commissioned, under construction and planned PCI projects to the power and gas systems. The section on the analysis of the power system presents the impact of PCI projects on market integration, CO2 emissions, renewable curtailment, marginal price, power adequacy, and welfare indicators. The impact of climatic variability on the calculated benefits provided by the 4th list of PCIs was also assessed for 2030. The section on the analysis of the gas system presents a similar approach on the evaluation of welfare indicators, adding insight on crisis scenarios simulating disruption of gas supply to EU through Ukraine, to assess the benefits of security of supply derived from the implementation of new projects.