1. Run a command prompt as an administrator. To do this, type
cmdin the search box, and when the cmd icon appears, right-click it and choose “Run as administrator.”
2. At the command line, type in the following:
powercfg -energy -output \Folder\Energy_Report.html
where \Folder represents the folder where you want the report to be placed.
3. For about a minute, Windows 7 will examine the behavior of your laptop. It will then analyze it and create a report in HTML format in the folder you specified. Double-click the file, and you’ll get a report — follow its recommendations for ways to improve power performance.
For more, check out this article.