iPhone 12 Pro battery drain at night

Have been observing a battery drain of 15-20% during idle time (6 hours), especially at night. However, its only 5-6% for the same duration during the day. Is this a common behaviour?

Have tried few things:

1. All background processes are off
2. Location services set for emergency, find my phone and apps while using only
3. Back-up has been switched off
4. White point set to 80%
5. No VPN
6. Notifications set to 2-3 apps
7. Switching off GPS, Bluetooth & Wifi either standalone or together
8. Force closing all app as instructed by Apple Support care
9. Hard reset and full a restore

But its still a consistent drain. Is there something I am missing?

If its not a common battery drain, any help would be much appreciated.

Thank you.