Originally Posted by
EnergyPlus There are several things that go on while you're phone is "sitting there." First, it's always looking for a tower, so if you're in a weak signal area, that will increase drain (and signal strength may vary from one room in the house to another. I once lived in a house where, the only place I could take/place a call, was from the NORTH edge of my dining room table, lol). Second, even though you have your apps closed, you may have some apps that do automatic updates/searches etc. at preset or scheduled times, or even routinely. For example, I have BerryWeather. Every hour, my phone updated the weather for the four locations I have set on the device. That takes some energy.
All this being said, your drain does seem a bit high for a phone sitting idle, so you may have apps running some service on a scheduled basis or, low signal strength. My phone, fully charged, will drain about 2-3% overnight, but no more.