A couple of quick things...
vCloud Director uses vSphere. If there's someone with vCenter access, they can probably run the PowerCLI snippet you linked.
Also, if this is an environment with vCenter Chargeback installed, you can grab some stats from there.
And finally, if you have an option for vCenter Operations Manager, it's handy to be able to glance at the Reclaimable Waste dashboard. Idle and Powered Off VMs are what you'd be looking for.
Where Idle Virtual Machines are defined as:
Time idle: 90 %
Detection based on all of the following thresholds:
- Average CPU usage less than: 100 MHz
- Average disk I/O usage less than: 20 KBps
- Average network I/O usage less than: 1 KBps