I would give it time like others have said.
On a side note, I have noticed a reduction in battery performance on my existing 12 Pro, might be an issue or glitch with 16.0/16.0.1.
One thing to note too, I forget where I read this but there was something mentioning a reduction in battery that was solved by disabling the weather widgets from the lock screen. Personally I like having it there but apparently, it is always updating and gathering location information, definitely worth a shot disabling it if you have it active.