The present invention relates to a modular electrical system (1) including a first current-emitting source module (2) and a first current-consuming sink module (4) which is connected to the first current-emitting source module (2). The first sink module (4) has a first sink identification means (4a) to identify maximum power requirement of the first sink module. The object of providing power balancing between a first source module (2) and a first sink module (4) is achieved in that the first source module (2) has a first source identification means (2a) for identifying the power capacity of the first source module, wherein in order to calculate a power ratio of the system (1) the first sink identification means (4a) and the first source identification means (2a) are connected to a two-wire line (6) for the purpose of generating a differential voltage (10).