Samuel Gibbs for The Guardian:
Using an iPhone 6S Plus for a week without the main Facebook app installed, I recorded the battery life at 10.30pm each day for a week comparing it to a daily average taken from a week with the app. I charged the phone overnight, taking it off the charger at 7.30am, and used it normally. I accessed Facebook for the same amount of time, and for the same purposes, using the social network’s excellent mobile site within Safari, as I had done using the app. I also left the Facebook Messenger app installed.
On average I had 15% more battery left by 10.30pm each day. I had also saved space, because at the point I had deleted the Facebook app it had consumed around 500MB in total combining the 111MB of the app itself and its cache on the iPhone.
"A Facebook spokesperson said the company was investigating the matter" – yes, yes I'm sure they are.