Abstract: For forwarding operation data related to the present operation of a plurality of inverter units which feed electric power from power generators into a power grid to a monitoring unit, the inverter units and a plurality of intermediate data handling units are connected to the central monitoring unit in a communication network of logical tree architecture. The tree architecture branches towards the inverter units, and several inverter units are connected to each intermediate unit. The operation data from each inverter unit are forwarded to that intermediate unit to which the inverter unit is connected; and, in each intermediate unit connected between the inverter units from which the operation data are forwarded and the monitoring unit, operation data of the same type forwarded from the inverter units connected to the intermediate unit are merged to reduce their data volume, and only the merged operation data are forwarded towards the monitoring unit.