In addition to the shortened battery life, the bug that seems to be affecting various handsets on iOS 14.2 also leads to longer charge times than usual. According to some users, their handsets (older ones in most cases, but also iPhone 12 models) lose over 50 percent in under 30 minutes. The 2018 iPad Pro also seems to be affected.
https://www.notebookcheck.net/Not-on-iOS-14-2-yet-Might-want-to-wait-for-the-next-update-because-this-one-causes-severe-battery-drain.508400.0.html