A modular electrical system including a first current-emitting source module and a first current-consuming sink module which is connected to the first current-emitting source module is provided. The first sink module has a first sink identification means to identify maximum power requirement of the first sink module. The object of providing power balancing between a first source module and a first sink module is achieved in that the first source module has a first source identification means for identifying the power capacity of the first source module, wherein in order to calculate a power ratio of the system the first sink identification means and the first source identification means are connected to a two-wire line for the purpose of generating a differential voltage.