The approach in this paper renders it possible to simulate large-scale smart grids by efficient parallel computations. This permits a detailed analysis of the consumption behaviours, efficiency and impact of green energies, and self-sustainability of a smart grid. The smart grid is modelled as a multi-agent system. Each agent represents a building which is optimally controlled. That is, an agents meets its prescribed energy demand by trading energy or applying devices, e.g. solar panels
and fuel cells, minimising its costs. A cooperative bargaining game is devised in which the agents participate to obtain a global optimal solution. In this paper, this inherently serial bargaining game is parallelised. The parallelisation is necessary to be able to deal with the large amount of data and computations which need to be performed. In the experiments the validity of the presented approach is shown and as a proof of concept a large smart grid of over 40 million agents is simulated.