There are some third party apps available that will let you display the battery percentage in the status bar, however it seems this may be something that arrives with a future update to Kit Kat. As it turns out, the battery percentage readout has been discovered hidden in Android 4.4, though, there are some quirks with the current implementation.
XDA forums member kroegerama has released an app that will allow Kit Kat users to enable this hidden feature. According to details on the XDA posting, this should work on any device running Kit Kat and users are not required to have root. Essentially, this app removes the underlying process of modifying code to change the setting.
Once the app is installed you need to open it, click the “Enable Battery Percent” option and then reboot your phone. Once the phone reboots you will have the battery percentage in the status bar, though, depending on the current level of your battery you may or may not see it. The battery percentage is white, and so is the battery icon.
Basically, the battery percentage number will remain hidden in the white on white until it drops down pretty low. You can get an idea of what it will look like in the image sitting above. Otherwise, given this app is modifying a hidden setting, you can actually uninstall the app after and not lose the percentage readout.
Those changing their mind after this has been done can also revert the process by launching the app and unchecking the setting. That all having been said, the developer did also offer a bit of explanation as to why he choose not to change the color from white.
“Sorry, this is impossible with a simple app like this one, because the color is hard-coded in SystemUI.apk. You need to decompile that apk, edit one line of source code and then recompile it. Actually, I don’t plan to do this, because I don’t like to change system-apps. Also, the OTA-Updates from google would fail after that and it would require root.”