The aim of this paper is to present mathematical models of all the propulsion components of hybrid drivetrains. These models are based on very limited amounts of data, nevertheless they match real characteristics with high accuracy based on numerous measurement data points, thus they allow the modelling process of fuel and energy consumption for a particular vehicle in any homologation driving cycle to be performed in a very short time at the early stage of vehicle design. The characteristics provided in the article concern: the full load engine torque curve, full load electric motor power curve, combustion engine efficiency characteristic, including dynamic states and warm-up period, electric motor efficiency characteristic, inverter efficiency characteristic, battery characteristics in a wide temperature range and efficiency of the drivetrain. Moreover, the main principles concerning gear ratio selection are provided to conduct subsequent steps of transmission modelling from scratch. Simulations of drivetrain performance and vehicle fuel consumption in WLTP and US06 tests prove the suitability of the presented models.