1. A method, implemented in a virtualized cluster system comprising a plurality of physical machines (PMs), for selecting a PM from the plurality of PMs as a migration destination for at least one virtual machine (VM) to be migrated based on calculating CPU voltage energy consumption of the PMs, the method comprising: identifying at least one VM currently deployed on a first PM of the plurality of PMs which is to be migrated to another PM of the plurality of PMs; for each of the PMs other than the first PM: calculating a CPU utilization ratio of the PM, wherein the CPU utilization ratio of the PM is a CPU utilization ratio of the identified VM to be migrated plus a sum of CPU utilization ratios of VMs currently deployed on the PM; obtaining a minimum CPU dominant frequency of the PM by multiplying the CPU utilization ratio of the PM by a maximum value of a dominant frequency of the PM; obtaining a pre-stored table comprising mapping relationships between CPU dominant frequencies and voltage values for the PM; obtaining a voltage value associated with the minimum CPU dominant frequency from the pre-stored table; and calculating a CPU voltage adjustment of the PM comprising a difference between the obtained voltage value and a current CPU voltage of the PM; selecting the PM of the other PMs with minimum relative CPU voltage adjustment as the migration destination, wherein there is at least one PM selected as the migration destination for one of the at least one VM to be migrated with a voltage adjustment greater than zero; and migrating the identified VM from the first PM to the selected PM and adjusting the current CPU voltage of the selected PM to the obtained voltage value.