A configuration system for reconfiguring a switch cabinet includes a detection unit—which detects functional units of an electric circuit, which are mounted within a switch cabinet, by way of characteristic features of the functional units, which have unambiguous identification features which are read out by the detection unit. A configuration unit contains a processor, which determines an electric circuit diagram of the electric circuit on the basis of the functional units of the electric circuit which are detected by way of the characteristic features and automatically replaces the detected functional units of the determined circuit diagram with associated replacement functional units which are stored in a database. An output unit is provided for outputting the determined replacement functional units.