Windows supports multiple power states defined in the Advanced Configuration and Power Interface (ACPI) specifications by the UEFI Forum. It is important to understand each one of them because depending on the hardware, the device may or may not support power-specific features, such as Hibernate, Fast startup, or modern power states like Modern Standby.
Although the computer may only appear to the user with two power states, including on or off, Windows supports different states that describe the energy consumption on each state, including Working, Sleep (Modern Standby), Sleep, Hibernate, Soft Off, and Mechanical Off. If you use a laptop or desktop computer, you can determine the supported sleep states using Command Prompt.
How to check which power sleep states are supported by your PC
To determine the sleep states available on your hardware configuration, use these steps:
- Open “Start”.
- Search for “Command Prompt”, right-click the top result, and select the “Run as administrator” option.
- Type the command powercfg /availablesleepstates to determine the supported sleep states of your computer and press the “Enter” key. The command can also be written as powercfg /a.
- Confirm the sleep states that are supported on the device. Available states include:
- Standby (S3)
- Standby (S2)
- Standby (S1)
- Standby (S0 Low Power Idle)
- Hybrid Sleep
- Fast Startup
Once you complete the steps, you will know the system sleeping states available on the device as well as those that are not supported.
System sleeping states on Windows
The information below describes all the possible sleep states available on Windows.
a. Working power state (S0)
The Working power state has an Advanced Configuration and Power Interface (ACPI) state of S0, and it describes that the device is powered on and usable. In this state, supported hardware that is not in use can enter into a lower power state to save energy.
b. Sleep (Modern Standby) power state (S0 lower-power idle)
This Sleep power state, also known as Modern Standby, has an ACPI state of S0 lower-power idle. It is available for some System On a Chip (SoC) devices that include a low-power idle state. While in this state, the device can switch from a low to a high-power state to quickly react to certain events. If the computer supports Modern Standby, it does not support sleep states S1, S2, and S3.
c. Sleep power state (S1, S2, S3)
Windows also supports the Sleep power state, which has the ACPI state of S1, S2, or S3. In this state, the device appears offline, but the system memory will continue to be updated to allow the system to resume to a working state. Some peripherals and hardware components will remain active, including network adapter, keyboard, mouse, and USB devices. You also have the Hybrid sleep mode in this category. In this mode, a hibernation file is created while using one of the sleep power states if the computer loses power during sleep.
d. Hibernate power state (S4)
The Hibernate power state has an ACPI state of S4. It describes when the computer is almost completely powered off, and the user can resume the session even after power loss. In this state, Windows will save the data loaded into memory to the hibernation file onto the hard drive, and some hardware will remain active (network adapter, keyboard, mouse, and USB devices) to wake up the computer as needed. You also have the fast startup mode in this category. In this mode, the user gets logged off before the hibernation file is created to save storage space and resume to a working state more quickly.
e. Soft Off power state (S5)
The Soft Off power state on Windows has an ACPI state of S5, and it describes the state between fully powered off and boot cycle.
f. Mechanical Off power state (G3)
The Mechanical Off power state has an ACPI state of G3, and it describes when the computer is completely powered off.
Note: While this guide lists all the possible power states when running the command, some states won’t be listed, for example, S0 and G3, even though they are supported.
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