Kubecost will display volumes unused by any pod. You can consider these volumes for deletion, or move them to a cheaper storage tier.
You can access the Unclaimed Volumes page by selecting Savings in the left navigation, then selecting Manage unclaimed volumes.
Volumes will be displayed in a table, and can be sorted By Owner or By Namespace. You can view owner, storage class, and size for your volumes.
Using the Cluster dropdown, you can filter volumes connected to an individual cluster in your environment.