Citizens Collaboration to Minimize Power Costs in Smart Grids - A Game Theoretic Approach Topics: Economic Models of Energy Efficiency; Greener Systems Planning and Design; Optimization Techniques for Efficient Energy Consumption; User-Centred and Participatory Design of Services and Systems for Smart Cities In Proceedings of the 4th International Conference on Smart Cities and Green ICT Systems - Volume 1: SMARTGREENS, 300-305, 2015, Lisbon, Portugal