Update: Oct 2015:
binned recycled the phone a month after my last update, it was incredibly frustrating to use with the battery drain. I now use a HTC one (M8).
That didn’t last long. Today I have had devastating battery drain. I give up.
My Sony Xperia Z battery drain problems resurfaced after 3 days of solid running. I had a hunch and just performed my last step of “managing data > clear all” and clearing the cache again and it immediately solved the drain again.
Something happens inside of the Google Play services package and causes my phone to be awake 100% of the time, what that is, I have no idea. but it seems the above advice sorts it out… for a while.
For anyone having the terrible battery drain problems since the 4.4 kitkat update from Sony / Google I have finally found a solution.
Download the latest Google play services app 5.0.82 (released yesterday 30/06/14) from the Google play store.
Strangely the store lists it as still being v4 and doesn’t auto update but it will let you manually press the update button. Odd, beta maybe?
Either way once you have Google play services v5 your Xperia phone’s battery drain issues will be cured.
I also cleared the cache and used the manage space option after updating which may have helped. I dont know.
I have decided to leave interest based ads turned off (as was suggested previously).
Play store auto updating and location are back on without battery drain issues you will be pleased to hear.
So far I have had 5 hrs standby with only 10% battery use compared to maybe 70-80% over the same amount of use pre update.
Whats next for the Xperia line? Its been problem after problem since I bought my Xperia Z back in April 2013…
-Ricky (written on my Xperia Z)