- From the Home screen, go to Settings.
- The battery can be tapped.
- Wait for the Battery Usage information to appear.
- Then go to the Show Activity page to see how much power is being used in the foreground and background.
- Tap on Battery Usage to see a % breakdown of your usage.
You can also see how healthy your iPhone X's battery is right now. This is one of the features of the iOS 11.3 beta. It displays information about your battery's maximum capacity when compared to when your device was new, as well as an indicator of how long your battery will last.
If you see any software or service using significantly more power than usual, that app is most likely the reason and should be managed or deleted if necessary.