Powering the device is a 2200 mAh capacity battery. Slightly bigger than the battery in the ZenFone 5 LTE, it wasn't quite as impressive.
We found the battery could last a day, but only just. With sync and WiFi/mobile data constantly enabled, the battery life was pushed to its limits. By the time we plugged it in in the evening, it was just about to fail.
It's fine for regular users, but heavy users might find the battery failing them earlier than they'd like.
As it is, the battery should get most people through a day, but not quite as impressively as the ZenFone 5 LTE.