While updates - of course - can sometimes introduce new bugs, etc. There are two things to take in mind 1) It is a known thing that after a phone upgrades for several days it might still be doing stuff in the background settling things and that may suck the battery 2) It might be possible that there's something misbehaving (check Battery Usage stats) in general and it just affects more with the new update because of obvious backend changes (meaning to say it might not be for everyone, just for whoever has app x or setting x.)