Virtualization solutions appear as alternative approaches for companies to consolidate their operational services on a physical infrastructure, while preserving specific functionalities inside the Cloud perimeter (e.g., security, fault tolerance, reliability). These consolidation approaches are explored to propose some energy reduction while switching OFF unused computing nodes. We study the impact of virtual machines aggregation in terms of energy consumption. Some load-balancing strategies associated with the migration of virtual machines inside the Cloud infrastructures will be showed. We will present the design of a new original energy-efficient Cloud infrastructure called Green Open Cloud.