The invention relates to a roaming method for an electrical charging system with at least two subsystems. In the method, a charging data set is received through a communication module of a gateway device from a charging station assigned to the gateway device. The charging data set is forwarded by a peer-to-peer module assigned to the gateway device to a peer-to-peer application of a peer-to-peer network, and a roaming action is controlled by a roaming controlling means of the peer-to-peer application executed by at least a part of the nodes of the peer-to-peer network based on the received charging data set.