Power grid models are important in relation to several topics and applications, especially the modelling, optimisation and extension of electrical grids. The significance of grid models is heightened by the increase in renewable energy generation and the challenges associated with its integration into the power grid. However, despite their crucial importance, grid models have generally not been made publicly available for scientific studies or technical analyses. Little information has been published about either the details and methods used in the derivation of these models, or their input and output data. Recently, several projects were initiated in an effort to address this by developing open source grid models and associated data. These projects used different approaches and methods, but most are based on the OpenStreetMap database. The goal of this paper is to compare the different available grid models on the basis of the structure and derivation methods used. Therefore, a novel combination of a graph-theoretical, Geographic Information System (GIS)-based and power-related comparison level is introduced using the open source tool AutoGridComp, which was developed by the authors. The grid models considered in this study are the Scientific Grid Model (SciGRID), GridKit and open street map Transmission Grid Model (osmTGmod) models for Germany.