By looking at opportunities beyond the single building scale, urban planners can significantly contribute to shape energy-efficient and low-carbon cities. However, the complexity involved in such a broad task and the many trade-offs with other sectors impede the realization of any simple solution. This chapter provides some background regarding urban planning and its relationship with energy issues. First, a systematic review of urban planning processes and common planning support tools and methods is presented. Second, a framework for analyzing the additional challenges of integrating energy in urban-scale planning processes is proposed. Finally, a discussion on the relevance and roles of simulation and optimization tools for supporting decisions in urban energy system planning is developed.