The CityGML Energy Application Domain Extension (Energy ADE) aims at extending the CityGML 2.0 standard with energy-related entities and attributes necessary to perform energy analyses at urban scale, such as energy demand diagnostics, solar potential study, simulation of low-carbon energy strategies etc... Its structure is conceived to be modular, so as to be potentially used and extended also for other applications (e.g. module Occupancy for socio-economics, module Construction and Materials for acoustics or statics, etc.). It consists of 5 modules: Building Physics module, Temporal Data module, Construction and Material module, Occupancy module, Energy Use and System module. The Building Physics module is the core of the Energy ADE. It extends the existing CityGML objects (Abstract Building, BoundarySurface and Opening) and related them to new thermal entities (ThermalZone, ThermalBoundary, resp. ThermalComponent). The Occupancy module is related to the CityGML model (AbstractBuilding) and Building Physics Module (ThermalZone). The Construction and Material, Energy Use and System, and Timeseries and Schedules modules are independent « floating modules » which may be connected to different CityGML and Energy ADE CityObjects. The ADE provides also a number of XML examples, illustrating how and where the Energy ADE entities and attributes may be embedded into CityGML.