Tourists today are more likely to be concerned with the environment and greener lifestyle choices. In this context, a green flagship of some hotels can be an important selection criteria at the time of selecting one. In the near future, buildings should become nearly zero energy, consuming as low as possible and producing almost all the energy they need, using renewable energy sources. To achieve this goal, hotel buildings need to pass through a transformation process that will make them more efficient. In this process, a decision support platform would be important to help hoteliers monitor their energy consumption, identify which points are consuming more than expected, decide which investments are more cost effective and manage their equipment in an optimum way. This chapter describes the challenges involved in developing such a platform, covering several research and development fields, including Internet of Things networks, ICT, Smart Grids, Renewable Energy, Energy efficiency, as well as algorithms for machine learning and optimization.