Some questions:
First of all, on setup, did you set up as new or from a backup?
Did you cycle the battery?
How is the coverage during the day? Low signal = low battery life
Did you turn off allowing apps to work in the background?
Mark the battery life, put the phone to the side for 20-30 minutes, if you see significant decline in percentage check what's eating the battery, there may be a rogue app operating constantly in the background
Worse case, restore and start new.
Good luck