Today, the preliminary design process of power system architectures of civil aircraft is usually characterized by the separation into Air Transport Association chapters. However, the complexity of an aircraft energy network, the large number of influencing design parameters, and system interfaces require a common and transparent process if a meaningful evaluation of different system architectures with regard to the overall aircraft efficiency is to be achieved. The development of a dedicated methodology, a simulation framework, and adapted modeling techniques are the objectives of the presented research. This paper focuses on the dedicated modeling approaches that are developed to analyze systems at the aircraft level. Three different modeling techniques illustrate, on one hand, the effort required to develop adapted models to fit in the proposed analysis environment. On the other hand, the added value of such an integrated modeling approach is demonstrated with the examples of the electric generator sizing analysis and the link of power system simulation to a global aircraft thermal model.