Use the Hidden PowerCfg Tool to Optimize Battery Life on Windows

The PowerCfg command is a hidden tool on Windows. Beyond just tweaking power-management settings, it can generate some sophisticated HTML reports on Windows 7, 8, and 10.

To use this tool, open an administrator Command Prompt window. On Windows 8, 8.1, or 10, right-click in the bottom-left corner of the screen or press Windows Key + X and select Command Prompt (Admin). On Windows 7, locate the Command Prompt shortcut in the Start menu, right-click it, and select Run as Administrator.

View Your Computer’s Sleep States

You can use PowerCfg to see the sleep and standby states your computer supports:

powercfg /a

Modern Windows 8.1 devices sometimes support something called Connected Standby. At least, it was known as Connected Standby in Windows 8 and Windows RT 8, but it was technically replaced by something called InstantGo in Windows 8.1. It’s still called “Standby (Connected)” in the powercfg list and elsewhere in the Windows operating system. Microsoft’s own documentation also muddles together Connected Standby and InstantGo, referring to them interchangeably.

If you see your computer supports “Standby (Connected)”, be sure to run a sleep study report with the below command.

Control Devices and Timers That Can Wake Your Computer

Your computer doesn’t just wake up when you press its power button. It may also wake up when a specific device tells it to — for example, when you move a USB mouse. Or, it may wake up due to “wake timers” programs set.

If you’re having issues with your computer automatically waking up when you don’t want it to, you can ask the powercfg command what last caused your computer to wake. You can also see a list of devices with permission to wake up your computer, and check if any programs have set wake timers that will force your computer to wake up later. You can then control whether these devices and wake timers can actually wake up your computer.

Generate an Energy Report

The PowerCfg command will observe your computer’s behavior for sixty seconds and then generate an HTML report with information about how power-efficient your current system state is. Trace down these issues and you can see exactly what’s draining your battery power more than necessary. Dig into them and you can potentially extend your laptop’s battery life.

The following command will generate an energy report:

powercfg /energy

Generate a Battery Report – Windows 8+

If you’re curious about your battery’s current state of wear, you don’t need a third-party tool. You can generate a battery report using the PowerCfg command. This includes information about your current battery’s actual capacity and how its capacity and battery life have decreased over time.

The following command will generate a battery health report:

powercfg /batteryreport

Generate a Connected Standby Sleep Study – Windows 8.1+

On devices that do support what Microsoft calls InstantGo and Windows itself calls Connected Standby, applications and devices on your computer are allowed to wake up the computer regularly to have it perform tasks. This is a lot like on a smartphone — while your phone’s screen is off, it can regularly wake up to perform tasks and stay connected to the network.

PowerCfg allows you to perform a “sleep study,” which will show you exactly which applications and device drivers on your computer are waking up your computer the most in Connected Standby mode. You can then try to prevent these applications from running and see which devices are the “worst offenders.”

To do this, run the following command. This only works if your computer actually does support Connected Standby:

powercfg /sleepstudy

There’s more to the PowerCfg command than this. For example, this is the command you’d use to disable hibernation and delete your hiberfil.sys file, if necessary. You can view a long list of options in this tool on Microsoft’s PowerCfg command page, although it’s incomplete. It doesn’t include the /batteryreport or /sleepstudy options, for example.

Chris Hoffman is a technology writer and all-around computer geek. He's as at home using the Linux terminal as he is digging into the Windows registry. Connect with him on Google+.