Anyone with a Nexus 5 has probably experienced the strange battery drain problem caused by the camera. It's mostly random, and that's one of the reasons it is so frustrating. We were hoping Android 4.4.3 and/or 4.4.4 would alleviate the issue, but it didn't quite get the problem fixed for everyone. Supposedly, all will be well soon.

The latest report indicates that Android L will fix the problem once and for all. This means we only have to wait a few weeks for Google to release Android L to our Nexus 5 devices. Here's a quote with some of the details,

One Google project manager blamed the Skype app, saying that an update to the Android version of the app caused it to screw up the mm-qcamera-daemon process, allowing it to get stuck, consuming the CPU cycles that ate away at the battery life of the stock Android phone. While there have been a few bug fixes for the handset, the problem still exists for some. Android 4.4.3 included changes to the camera that did take away the problem for many. For some though, the rapid draining of the battery continues.
It's almost frustrating that it has taken so long to knock out this problem. I guess it's better late than never...

Source: PhoneArena