Estimating Battery Life

If you are using a laptop computer, you probably already know that the battery in that computer has a limited life. Due to any number of different variables, your battery "wears down" over time and eventually refuses to charge up.

If you are using Windows 8 or Windows 10, you can use the powercfg utility to generate a "battery report" that provides an estimate where your battery stands in its lifecycle. While the powercfg utility is available in Windows 7, it doesn't include the capability to run this particular report.

The powercfg utility can be run from the command line, but you need to make sure that you open the command prompt window as an administrator. Here are two easy steps that allow you to do that:

1. Use the search capabilities of Windows to search for cmd. As you type it, you should see a single command shown on the screen, for cmd.exe.
2. Right-click on cmd.exe and choose Run as Administrator from the resulting Context menu. This opens up a command line prompt window.

Now you can enter the following at the command prompt:

powercfg —batteryreport —output c:\report.html

The report takes a while to generate as powercfg tries to figure out the status of your battery (or batteries, in some systems). When completed, you can use Explorer to navigate to where you told powercfg to store the report (the C:\ drive in the above example, in the file named report.html). Double-click the file and it should open right up in your browser.

As you look through the report, you should see a ton of information. The section you want to focus on, however, is the one entitled "Battery Life Estimates." This section provides information that tells you how long you were able to use the battery and how long you should have been able to use the battery between each charging.

The information in the report allows you to see, over time, the performance of the battery. When that performance degrades to an unacceptable point, you can figure out when it is best to replace it. The report doesn't give recommendations as to when that should occur, it simply provides you with the data so you can make the determination yourself.

 This tip (13464) applies to Windows 8 and 10.