I usually put my phone on battery saving when going to bed at night. I have noticed that if I switch off the internet (both WiFi and mobile), battery goes down about 1-2 %. However if I do the same but with internet activated, battery goes down about 10%.
I have taken a look to the battery stats (see image) and there are a lot of “active” activated in the middle of the night. How can I know what apps activated the phone? Maybe I could make more of my battery life.
I would suspect it’s apps looking for updates and/or calling home to send some reports (like hiccup does).
You really should check the data useage like @paulakreuzer posted.
Then you can check what the active apps are allowed to do. Should they check for updates, that’s useful, otherwise, I am not so sure.
You could use BetterBatteyStats and there check which wakelooks and proccess are most present during night (you can manually set a reference time before going to night).