The Efficiency badge is the last major badge and it shows us how efficient we are with our resources in terms of rightsizing and target density ratios.
Issues related to efficiency are rarely issues that you would need to be alert of; however, they are useful to report and ensure that you are getting the most out of your infrastructure.
The Reclaimable Capacity badge is a graphical representation of the amount of unused computing resources currently assigned to your virtual machines.
In vSphere, Reclaimable Capacity is only applied to virtual machines, as it is seen that VMs are fairly straightforward to rightsize as requirements keep on changing in the environment. The same could not be said for hosts, for example, adding or removing resources from a physical host based on the demand would not be seen as a common task.
Although Reclaimable Capacity only applies to virtual machines, objects such as clusters, hosts, datastores,...