Yeah the problem only happens when ART is turned on, when switching back to Dalvik battery life is better and it doesn't update after every reboot.
Edit - I've tried 3 factory resets and switched between Dalvik and ART around 6 times, with no luck.
Hey, Thanks for your detailed reply! :) Unfortunately clearing the cache didn't work, one other thing I should probably mention is that when I switch to ART the battery drops probably 1% every 30 seconds with the screen on.
I turned ART on my Moto G, and now whenever I reboot the phone, it says 'Android Is Upgrading' is this just because ART is an experimental feature or is there something wrong with the phone? Thanks in advance :)