In the perspective of the large-scale application of the Moroccan Thermal Construction Regulations (RTCM) to existing buildings, eco-districts represent an ideal framework to initiate, test, and evaluate such an action. This study aims to present a methodological framework to improve the decision-making process for the energy upgrade of a future eco-district transformation. The case study of a neighborhood in northern Morocco shows that thermal insulation of buildings allows a significant reduction of energy needs that can reach an average annual gain of 52.72% compared to the existing situation. While installing PV systems on 50% of the roof surfaces allows a more critical improvement of the obtained gain: the average annual income in the case of monocrystalline PV can reach 108.14% and 94.87% for polycrystalline PV at the scale of the district.