It seems this happens after every Android update for a lot of users... but then the complaints seem to go away after a while. I think multiple restarts are a big factor in how quickly a new Android update settles in. I restart my phone every night, and do multiple restarts after an Android version update (as well as security updates), and I've been fortunate enough to never experience any battery drain.
Also, if you can, do a cache partition wipe... I do those after every update as well if the phone will let me

And in the worst case scenario, I've seen a factory reset fix the problem

But then the nuclear option tends to fix most problems lol.