The Facebook app consumes a lot of power even when it is running in the background. Once the app was uninstalled, the Android system and Android OS both consumed less battery power. Even if Facebook doesn't show up on your phone as a power hungry application, the battery life it is munching on will show up elsewhere.
If having a longer battery life is more important to you than using the Facebook app, why not uninstall it and use your browser if Facebook is needed? You will be thanking yourself for doing so the very first time that your phone is running on fumes.
source: Reddit via TheGuardian