Pervasive information and communication technologies and large-scale complex systems, are strongly influencing today’s networked society. Understanding the behaviour and impact of such distributed, often emergent systems on society is of vital importance. This paper proposes a new approach to better understand the complexity of large-scale participatory systems in the context of smart grids. Multi-agent based distributed simulations of realistic multi-actor scenarios incorporating real-time dynamic data and active participation of actors is the means to this purpose. The Symphony experiment platform, developed to study complex emergent behaviours and to facilitate the analysis of the system dynamics and actor interactions, is the enabler.