When Power saving is enabled in a cluster it distributes the load in a way that consolidates virtual machines on a subset of available hosts. This enables surplus hosts that are not in use to be powered down, saving power. You can set the threasholds in the RHV-M GUI to specify the Minimum Service Level a host is permitted to have.
You must also specify the time interval in minutes that a host is permitted to run below the minimum service level before remaining virtual machines are migrated to other hosts in the cluster - as long as the maximum service level set also permits this.