Tip: Windows 7′s Hidden Power Efficiency Report2
The battery indicator built into Windows is about as barebones as it gets: it provides a percentage remaining in battery life, an estimated time left, and an option to switch power plans. The time remaining is calculated using the battery’s historical usage data (such as longest possible run time) and how much system resources are being used. With the hidden Power Efficiency Report built into Windows 7 (and now 8), it’s possible to check out at what exactly Windows is looking at when it determines your battery usage, and at the same time see what you can do to make your battery last even longer.
Open a command prompt window under Administrator privileges and enter “powercfg -energy“. For the next 60 seconds, Windows will trace your system behavior. Continue using your computer normally until the command prompt window says “Analysis Complete.” The report has now been generated in the following file:
Open it up in your favorite browser to view the power efficiency report. In the report, you be provided with warnings and errors about system behavior, and what applications have the most CPU utilization. Changing your settings and behavior to what the report recommends can increase your battery life from a few minutes to possibly even a few hours.
In some cases, the report lists items that are too specific or are simply unchangeable, so not everyone will find it useful. Windows 8 included no improvements to the power efficiency report from Windows 7, so the feature has likely been scrapped, which would explain why it can only be found in command prompt.