Method for operating a modular electric system

The method involves connecting several source modules (2-4) and sink modules (5-8) in parallel to each other. The source modules are provided to supply electrical power to sink modules for power-redundant operation. The total electrical power demand of sink modules, and total electrical power output from the source modules are determined and displayed by evaluation unit (12). The total electrical power demand and total electrical power output are tested so as to provide equal electrical power output with respect to electrical power demand of sink module. Independent claims are included for the following: (1) modular electric system; and (2) evaluation unit.