Cities can play a key role in mitigating climate change impacts, as they represent two thirds of the world’s energy consumption and greenhouse gas emissions. This paper presents a model-based approach to support cities in the challenge of including energy issues in early stage urban planning. Recognizing that successful planning must rely on highly integrated solutions, this paper aims, through its approach, to better understand and reinforce links between generally fragmented sectors, scales, stages and disciplines. Considering the planning framework of the Swiss canton of Geneva, the main planning instruments are presented and an in-depth analysis of the urban and energetic goals and constraints is carried out. Linking the disciplines of planning and optimization, a Mixed Integer Linear Programing (MILP) model is formulated to identify optimal energy strategies, as well as to provide insights into the urban layout, distribution and size of buildings. Additionally, this approach aims to overcome one of the difficulties of early stage planning, where information regarding energy is scarce. In this regard the proposed methodology generates building information based on available data and constraints. The simultaneous consideration of multiple scales allows to assess the interactions of building scale decisions with overall district energy supply alternatives. The resulting depiction and quantification of trade-offs should allow planners to anticipate optimal energy system configurations and adapt their plans accordingly.