The paper is devoted to the analysis of the losses in the drive system of the Nuna. The Nuna is a solar car that won the World Solar Challenge (WSC) a few times. The objective of this paper is to model and quantify the losses in the drive system of the Nuna, to validate this model by means of measurements, and to use this model to investigate if a decrease of the losses is possible. The losses in the drive are modelled to determine the optimal solar car parameters. In this model the losses of various components of the drive are described with equations that are a function of determinable and measurable quantities. In this way the model is suitable for calculating the losses that occur during the driving of a trajectory with a certain load to the drive.