To conserve power when not using the computer, you generally have 3 options: shut down, hibernate or sleep. The state of open documents and applications running is preserved when sleep or hibernate modes are used. However, booting up is faster from sleep than from hibernate because contents of the RAM are preserved. Hibernate uses less power than sleep because contents of the RAM do not need to be preserved; they are saved on the hard disk. Hibernation is similar to regular shutdown but without the unnecessary hassle of terminating all open applications.

Comparison chart

Hibernate versus Sleep comparison chart
Edit this comparison chartHibernateSleep
Processing Functions Closed and saved to hard-disk Stopped and saved in RAM
Power usage Zero power Low power consumption
Resumption Slow Instantaneous
When to use When the system is idle for longer time and rebooting after shut down will be tiresome or inconvenient. When the system is idle for a short time
Operating Systems supported All OS where the hardware is ACPI enabled including Windows, Mac OS X and Linux All OS where the hardware is ACPI enabled including Windows, Mac OS X and Linux
Also known as Suspend to disk (Linux), Safe Sleep (Mac), S4 in ACPI Standby (older versions of Windows), Suspend to RAM (Linux), S3 in ACPI
Power button and standby light indicator
Power button and standby light indicator

State of the computer

The state of the computer upon resumption is the same before it enters hibernate or sleep mode.

During hibernation, the hardware is completely powered down while the computer retains its state. Similar to shut down, a hibernating system needs more time to start up. On start-up, data is read back to the RAM which takes about 10 seconds or more. Hibernation provides the advantage of eliminating the need to save data before shutting down and restore the applications on power up.

During sleep mode the computer cut power to subsystems that are not needed and places RAM into minimum power state. As a result the resumption on waking up is instantaneous. Only the CPU and the display need to be powered up. Most laptops enter this mode when the machine is running on batteries and is closed.

Pros and Cons

A speed test of switching from sleep/hibernate mode to resume mode is performed in this video:

Operating system support

Hibernate and Sleep modes are supported in all operating systems where ACPI is supported. Hibernate is defined as S4 in ACPI and sleep as S3.

Some of the options available for Hibernate and Sleep in various OS are:

Operating System Hibernate Mode Sleep Mode
Windows Hibernate - available since Windows 2000
Hybrid Sleep - introduced in Windows 7
Hybrid Boot - introduced in Windows 8
Suspend - Windows 95
Standby - Windows 98 - 2003
Sleep - Windows Vista and later versions
Mac OS XSafe Sleep Sleep
LinuxSuspend-to-disk option Suspend or suspend-to-ram option


Hybrid Sleep mode is a mix of sleep mode and hibernate, where the contents are stored in RAM and hard drive. The RAM stays powered during power down. The restart is faster (contents retrieved from RAM) and with minimal power loss. During a complete power loss (power outage scenario), when RAM is offline, data is retrieved from the hard drive.

Hybrid Boot mode where the user is logged out before hibernating, thereby drastically reducing the size of the hibernation. It hence takes less time to write to disk and resume.


In the Advanced Configuration and Power Interface (ACPI) specification, hibernation is called suspend-to-disk and is the S4 power state in the standard. And sleep (also called standby or suspend-to-RAM) is the S3 power state.


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