Windows Hello, the biometric authentication system in Windows 10, might actually be the culprit behind the unusual battery drain of the new Surface Pro 4 as well as Surface Book while both devices are in sleep mode. At least, this is the phenomenon (and not a good one, we might add) that several owners of either device go through whenever their Surface Book or Surface Pro 4 are put to sleep or sent to standby mode. Of course, this has not been singled out to be the main cause just yet, but it does seem to be the most likely culprit.
For those of you who are proud of your new Surface Pro 4 or Surface Book, but have encountered this rather infuriating issue, then perhaps it would be in your best interest to turn off Windows Hello according to the forum. In order to make that happen, here is what you need to do. Head to Settings > Accounts > Sign-in options, and go ahead by removing facial Windows Hello login. Hopefully through this, the battery life on your device should increase so that your device experiences the right sleep/standby process.
At the end of the day, nothing beats a good and proper fix from the official party, and the onus falls squarely on Microsoft’s shoulders for sure.