Explicit simulations of the building heating and cool-ing loads at the district scale is hard to achieve be-cause of their huge computational cost and the lackof relevant data at such an urban scale. A commonsolution to answer both problems is to simplify themodel, usually resulting in a lower accuracy. This is-sue rises the following question: how to design a dis-trict energy model given computational limitations ? A specific modelling and simulation platform, calledMoDEM (Modular District Energy Model), was de-veloped to answer this question. The level of details of the model is modular in order to fit the available dataor the available computational resources. For bothcases, the impact of the assumptions can be evaluatedas well as the loss of accuracy. To illustrate the pos-sibilities offered by the platform, a district is takenas a use case. The results are discussed regardingthe effects of various model adaptations on simula-tion outputs. The introduced methodology evidencesthe steps making it possible to reach explicit simula-tions of the energy load of a district and demonstratesthe ability, and the limitations, of current tools