Droplets that are powered off still incur hourly charges.This is because the hypervisor continues to reserve your share of CPU, RAM and disk (as well as the IP for your VPS).
If you would like to discontinue using a droplet while preserving it for later use, we recommend taking a snapshot of the droplet and then destroying it. Please reference `Step One` from the following community article for this process: https://www.digitalocean.com/community/articles/how-to-resize-droplets-using-snapshots
After you have taken a snapshot, you can build a new Droplet from that snapshot image at any time in the future. Again, you can refer to the earlier community article to help you through the rest of the process: https://www.digitalocean.com/community/articles/how-to-resize-droplets-using-snapshots
When you are ready to use it again, you can create a new droplet from that snapshot. The only difference would be a new IP address.