A DRS cluster can be configured to change the power state of the selected hosts, in order to reduce the power consumption by the cluster. This feature is called the vSphere Distributed Power Management and is configurable only if the cluster is DRS-enabled.
The following procedure will help you enable and configure DPM on a DRS enabled cluster:
From the vCenter's inventory home, navigate to the Hosts and Clusters view.
Select the cluster and navigate to Manage | Settings | vSphere DRS and click on Edit.
On the Edit Cluster Settings page, click on Power Management to expand it and view the sub-settings. Note that the default setting is Off. Select either Manual or Automatic automation level.
Click on OK to acknowledge the warning and enable power management.