Update 2 (October 12):
One of the experts updated that the Photo app’s excessive mobile data consumption issue has been reported to Google as a bug.
Update 1(August 21):
An expert on the official Photos forum informed the affected users on August 7, that
“A bug report has been filed with Google, which does not report back to us on progress with fixes”
So, it’s clear that Google is aware of the issue, but the company is yet to officially acknowledge it.
Original Story below
Experiencing speedy consumption of mobile data? Well, if you have Google Photos installed, the app may well be the culprit.
The issue dates back to January, 2016 when it was reported for the first time. Those who faced the problem, state that after receiving the data exhaustion notification, their device settings confirmed that the Photos app has rapidly used maximum part of their data limit.
Not that you can’t disable Google Photos from using cellular data, but users say the option, when enabled, has no affect, as the app still consumes mobile data. Both iOS and Android users are facing the problem – some Android users even say turning off the ‘Background data’ feature also has no affect on the data consumption by the app.
On June 14, 2017 iOS users finally got to hear from an expert at Google Photos forums that
“I’m escalating this issue to an experts group on this forum”.
Another expert added
“with multiple people having the issue it does look like there might be a problem in Google Photos and will try to find out more on this issue”.
There was no update after that.
It appears that the issue has been escalated and might get fixed soon. If you have been encountering the same problem on your device, keep a tab on this post for further updates. Meanwhile, you can try selectively turning off cellular data for Google Photos, as it’s the only suggested workaround.