Iphone 14 pro battery drain at night

Your phone uses energy continuously, as long as it isn’t powered off. This means that if it is not connected to power for 8 hours the battery level will be lower at the end of that time. How much lower depends on what apps you have, how many notifications you have enabled, and, probably most important, how strong your cellular signal from the network is. You should be charging your phone overnight.

The absolute best way to get maximum use on a charge, as well as slow the decline of battery capacity long term is to enable Optimized Battery Charging (Settings/Battery/Battery Health) and charge the device overnight, every night. The battery will fast charge to 80%, then pause. During the nighttime pause the phone will use mains power instead of battery power, allowing the battery to “rest”, and thus reducing the need to charge the battery quite as often. The phone will resume charging to reach 100% when you are ready to use your phone; it will “learn” your usage pattern. If you enable iCloud Backup (Settings/[your name]/iCloud - iCloud Backup) the phone will back up overnight also, assuring that you can never lose more than the current day’s updates. Here's more information→About Optimized Battery Charging on your iPhone - Apple Support

Go to Settings > Battery and look at the apps that are using the battery. I suggest charging the iPhone at night.