This report, commissioned by France’s Ministry for the Ecological Transition and written jointly by the International Energy Agency and RTE, the French Transmission System Operator, examines the conditions and requirements needed to assess the technical feasibility of scenarios with very high shares of variable renewable energy in France’s power system. The report looks into trends for energy demand and renewable resource availability in the 2020 National Low-Carbon Strategy (Stratégie nationale bas-carbone, or SNBC). Several scenarios of high shares of renewables are examined: mainly based on onshore wind, mainly based on offshore wind expansion and mainly based on distributed PV. Building on these scenarios, the report looks at changes in the system’s flexibility needs and how the range from short-term to long-term flexibility can be satisfied by new technologies such as flexible charging of electrified transport, battery storage, demand-side flexibility and sector coupling. The report then looks to essential questions on electricity security, i.e. addressing the issue of keeping system stability in the context of decreasing system inertia, ensuring adequacy of the system and the sizing available reserves under a scenario of large shares of variable renewables. Finally, the report evaluates the VRE integration capacity of the existing French transmission network, as well as necessary modifications and expansion beyond 2035. The recommendations and findings of this report form the basis for further detailed technical and economic assessments that are to be carried out by RTE in 2021.