Abstract— Distributed generation (DG) of electricity is providing an increasing part of the worldwide electricity supply. At the same time, there is a big potential of demand response resources. When — in a geographical area or in the contract portfolio of an energy trader — the number of these Distributed Energy Resources (DER) increases, clustered control of DER by common ICT (information and communication technology) systems can add value. Due to the fine-grained and distributed nature of DER, the design of such a system needs to meet heavy requirements, e.g. regarding scalability and openness. Further, these systems need to balance multiple stakes in a multiactor environment. Multiagent systems, especially those based on electronic markets have been identified as key technologies in this respect. This paper presents a multiperspective case study of the design, implementation and performance of such a system for the business case of imbalance reduction in commercial clusters...