I take it you have checked the task manager for active processes? And have you checked the battery capacity and actual power draw, or are you inferring power draw from the battery life? Something like batterybar will tell you capacity and current draw (averaged over the past minute or so). As an example, below is what I get when I hover over the batterybar indicator. It shows 16W draw at the moment (pretty high, because Windows Search is running at 16% CPU for some reason..) and it shows the actual battery capacity. That way you can make a better estimate of what to expect.