This paper describes a framework for parametric modelling of hybrid-electric powertrain components for innovative airplane configurations. These models are used in scalability studies and performance analysis of novel propulsion architecture. The methodology involves culmination of these models in a set of tools specifically developed to study the initial and conceptual sizing of hybrid-electric aircraft. This allows quick parametric evaluation of various configurations based on components at different technology readiness levels, such as batteries and fuel cells. Characteristics and performance of the power-train components are evaluated using computational analysis as well as laboratory tests. This information is used to develop numerical models described in the paper and to validate the sizing of fundamental propulsion components. Applications to two variants of a commuter aircraft are given, one using a serial hybrid-electric architecture based on a thermal engine, and the other using a fuel-cell system fed by a gaseous hydrogen tank.