Distributed Power Management - enables to consolidate virtual machines onto fewer hosts and power down unused capacity - reducing power and cooling. This can be fully automated where servers are powered off when not needed and powered back on when workload increases.

Enterprise Plus, Enterprise only; Standard: DPM - n/a

Host Power Management (HPM) : ESXi 5.5 provides additional power savings by leveraging CPU deep process power states (C-states). In vSphere 5.1 and earlier, the balanced policy for host power management leveraged only the performance state (P-state), which kept the processor running at a lower frequency and voltage. In vSphere 5.5, the deep processor power state (C-state) also is used, providing additional power savings.

Please note that HPM and DPM are independent from each other, DPM controlled by vCenter and HPM by the ESX hypervisor