The goal of this research project is to investigate the current and future usage of the electricity transmission grid in the context of the energy transformation. To this end, the project develops methods to allocate short- and long-term network costs based on the individual network usage. Specifically, it proposes algorithms for power flow allocation and carries out a systematical assessment and comparison. The algorithms will be made freely available as a software package in an open model of the power system. Based on these flow-allocation algorithms, the project develops and evaluated methods for the allocation of network costs. These allocation schemes will be implemented into existing models of the German and European electricity markets and networks in order to investigate their implications the short-term operation and on the long-term investment decisions of market participants.