Board Thread:Troubleshooting/@comment-14.2.159.113-20191006054630/@comment-38015773-20191006060431

I think it's 1 energy unit per 3 minutes. The higher your rank, the longer it takes to fully charge. To reach 470 (from 0) would take 23:30. You can try using the talismans that speed up regeneration, even when you don't have the game "open."