Root Out Power Hogging Applications Using Microsoft's Sleep Study Tool For Windows 8.1
Sleep Study is part of the powercfg.exe utility in Windows 8.1 and RT 8.1. It's designed to tell you how well the system slept and how much activity it experienced while in a sleep state. As you know, there's still activity taking place when your system is in sleep mode, it just happens at a much lower frequency. The Sleep Study tool lets you track what's happening and potentially root out offending applications that might be having an overly negative effect on battery life.
"You can use Sleep Study to see which apps and devices are most active during a sleep session. Sleep Study reviews all the sleep sessions longer than 10 minutes and provides you with a report that color codes each session according to its power consumption," Microsoft explains in a blog post. "A session is defined as the period from Screen Off to Screen On. In cases when the system is plugged into AC power, the policies are less stringent than when on battery power. While the tool still tracks connected standby activity on AC power, it is more useful to identify unexpected drains on battery, or DC power."
Bear in mind that Sleep Study only runs on systems that support InstantGo. If you're unsure, fire up a command prompt and enter powercfg /a. This will give you a list of the available sleep states, including InstantGo, which will be listed as Standby (Connected) in the command prompt.
For more details about Sleep Study and information on how to run it, reference Microsoft's instructions here.