This chapter provides a vision of the increasing energy problem in computing facilities with focuses on cloud computing, under the new computational paradigms, and proposes solutions from a global, multilayer perspective, describing a novel system architecture, power models, and optimization algorithms. Researchers have done a massive amount of work to address the issues and provide energy-aware computing environments. Consolidation allows reducing the number of operating servers to process the same workload, minimizing the static consumption, which leads to operating server set and turn-off policies. Cloud computing, mobile cloud computing, or even modern high-performance computing start with data centers. While we can dream of a world in which anyone is allowed to sell their excess computing capacity as virtualized resources to anyone else or where the ubiquitous sensing of information is processed by a center kilometers away from the source.