Android Marshmallow Devices Must Divulge All Battery-Related Stats To Gain Google’s Blessing
The new policies are laid out in Google's Compatibility Definition Document (PDF) for Android. In section 8.4 labeled Power Consumption Accounting, Google lays down the law by stating devices running Marshmallow "MUST be able to track hardware component power usage and attribute that power usage to specific applications." This means you'll be able to see how much battery life individual apps are consuming.
There are several other related requirements laid out in the same section, including what power value to use (milliampere hours, or mAh). However, being transparent with battery auditing on a per app basis isn't the only new requirement for devices running Marshmallow.
Google also requires that Marshmallow devices use a new feature called Doze. It's a power saving feature that automatically puts phones and tablets in sleep mode when the display is turned off and they're not charging or moving. Doze doesn't disable background services, but it does defer certain battery sucking functions.
The policies related to battery life and transparency are a bit more aggressive in Marshmallow than previous versions, though not surprising since that's been an area of emphasis when talking up the latest release.