The transition to regenerative energy resources paves the path from a small number of large power plants to a grid of highly distributed, heterogeneous small generators. To establish a Smart Grid it requires a scalable machine-to-machine communication that allows to control and coordinate millions of energy producing and consuming devices. In this work we contribute a future deployment concept of a scalable communication infrastructure for Smart Grids. Our proposal is based on group communication utilizing hybrid multicast over public networks. We show by real-world measurements that our approach achieves high scalability while also limiting end-to-end communication delay.