Here is an interesting finding observed by some Surface Pro 4 users. According to them their devices Surface Pro 4 are experiencing unusual battery drain when the devices are being put to sleep or standby.
Here is the observation:
It clearly shows Hello is responsible for this.
So what’s the workaround?
Until Microsoft comes out with a permanent fix you can try to disable Windows Hello. To do this:
Settings > Accounts > Sign-in options >remove facial Windows Hello login.