There's no shortage of battery monitoring applications in the Play store. Each of these apps offers different solutions when it comes to viewing your battery's percentage. Some add an icon to the status bar, others can place a widget on your home or lock screen, and some even place a permanent notification in the notification shade. While all of these solutions work, none is ideal.
Android should support this natively, without requiring a third-party app; I know I'm not alone in thinking this. Thankfully, it looks like Google is finally working on adding a battery percentage feature to Android 4.4 KitKat devices, but it doesn't appear to be quite complete yet. According to a post on Android Police, the feature can be enabled with the use of a single ADB command, or by installing an app -- both methods being possible without rooting your device.
Once the native battery percentage is enabled on an Android 4.4 device, you may not be able to find it. The reason is because of the way Google currently has implemented it. The percentage is located within the battery and shares the exact some color of the battery, white. So if your battery is above 50 percent you won't see any numbers present, but as your battery drains you'll begin to see the numbers.
The ADB command to enable the battery percentage is:
adb shell content insert --uri content://settings/system --bind name:s:status_bar_show_battery_percent --bind value:i:1
For those Android users who aren't comfortable with using ADB, you can download a simple app from this XDA forums post that allows you to enable or disable the percentage using only your device.
It will be interesting to see what the final implementation looks like from Google. I, for one, don't mind the percentage being visible only after a certain point. It prevents me from staring at a number, even if it's in the 80s, and analyzing if I should charge now or later.