Current Build: 4.4.2
As of last week, I start to notice the battery life on my Nexus 5 starting to drain much faster than usual. As noted when I first received my Nexus 5, I can get more than 1 day of usage out of the phone. Now it would drain down to 20% if I don't charge it throughout the day.
It seems like "Cell Standby" is using most of the battery drain... which is strange as it has never been the culprit in the past. I am with AT&T, so I wonder if its something AT&T has changed recently to it's cell towers in NYC since this was not the case few months ago. It seems like this is a common complaint.
[UPDATE]: I turned off "LTE" (in settings>more>mobile networks>preferred network type>3G) so it is forced back to 3.5G HSPDA which offers much stronger signal, 5 bars. This seems to have restored the battery life as I once expected. Still not sure why the sudden problem with LTE as it has not been a problem until recently.