If the phone is new, battery will require "breakin" period. If that's what it is. That's about where I started with mine, got down to about 7-9% pre-portico and now I have about 3%/hr on Att Lte. I regretted buying phone due to the abysmal battery life at first, but now its better than my BB 9810. So I can't complain.
I actually did a factory reset on a full charge after about a week on Portico and whether coincidence or not, I went from 7-9% to 3-4% overnight and I have been able to turn on all of my email accounts, notifications and background services since reset and keep 3%. Try soft reset every morning and see if it gets any better. If not might give hard reset a try but beware, there were issues with hard reset earlier. Nokia may have resolved them with portico. Search forums for info. Seemed to have the most impact on mine.
I would give it a couple of weeks unless you are in 14day window with carrier. I returned first 920 on 14th day due to battery concerns. #2 wasn't any better than first so I stuck with it and now I have great battery life for LTE.