This option is visible only when there are one or more power associations to the target, when the target power is on (port status is up), and when user has permission to operate this service.
Provided you have privileges to do so, you can manage power from the Virtual KVM Client (VKC) and Active KVM Client (AKC) as well. See Remote Power Management via Virtual KVM Client (VKC) or Active KVM Client (AKC)