This work focuses on the feasibility of a 19-passenger hybrid-electric aircraft, to serve the short-haul segment within the 200–600 nautical miles. Its ambition is to answer some dominating research questions, during the evaluation and design of aircraft based on electric propulsion architectures. The potential entry into service of such aircraft is foreseen in 2030. A literature review is performed, to identify similar concepts that are under research and development. After the requirements definition, the first level of conceptual design is employed. Based on a set of assumptions, a methodology for the sizing of the hybrid-electric aircraft is described to explore the basis of the design space. Additionally, a methodology for the energy storage positioning is provided, to highlight the multidisciplinary aspects between the sizing of an aircraft, the selected architecture (series/parallel partial hybrid) and the energy storage operational characteristics. The design choices are driven by the aim to reduce CO2 emissions and accommodate boundary layer ingestion engines, with aircraft electrification. The results show that it is not possible to fulfill the initial design requirements (600 nmi) with a fully-electric aircraft configuration, due to the far-fetched battery necessities. It is also highlighted that compliance with airworthiness certifications is favored by switching to hybrid-electric aircraft configurations and relaxing the design requirements (targeted range, payload, battery technology). Finally, the lower degree of hybridization (40%) is observed to have a higher energy efficiency (12% lower energy consumption and larger CO2 reduction), compared to the higher degree of hybridization (50%), with respect to the conventional configuration.