What version of FVE are you running? You do not need to create any service. There is an Out of the Box report that you can run:   [IMAGE] [IMAGE] 
I tried to achieve this by adding my cluster into a new service and then running a report on that cluster but didn't work. Do I need to add the VM;s as well in the service to fetch this report. Kindly advise.
How to Fetch a report to list all the VM's which are powered off in a cluster.