iPhone 8 with 14.2 installed. Charged to 100% Then had WiFi, Bluetooth and Cellular turned off, Airplane Mode on and completely powered off. In six days (this was a planned test) it went down to 30%. Checked battery activity and nothing was listed for that time period. Not sure if the battery is actually draining or this update is just calculating it incorrectly. I have no problems with my iPad Pro on the same version of software.