What is Sleep Mode in PC? Pros, Cons & More

What is Sleep Mode in PC?

Sleep mode in computers actually refers to a specific type of power saving option when the PC enters into a low-power state when it is not in use. In simple terms, it is the low-power mode of a PC which helps in saving power.

Technically, in this mode, the Central Processing Unit and other components are powered or shut down, thereby using no power, but the state of the PC is kept in memory.


  • Sleep mode is a specific type of power-saving feature which is available both on modern desktop and laptop computers.
  • In most devices, this particular type of power mode is indicated by a pulsed or red-colored LED power light.
  • In this particular mode, all power-hungry components are sent to their lowest possible power state to save energy after a set time of inactivity.
  • It is only the RAM of the PC that gets the necessary power to retain the contents and is therefore refreshed incessantly.
  • A computer can wake up from its sleep mode when the mouse is moved, any key is pressed on the keyboard, or even when an object falls on it.

Understanding Sleep Mode

What is Sleep Mode

Sleep mode signifies the power-saving state of the computer when the unneeded components are shut down, but not the RAM, so that it can retain the required data stored in it.

Most computing devices and computers today are designed to enter into the sleep mode when they are not used for a certain period of time, which, however, can be set manually.

In fact, this energy-saving mode is typically the current norm for power management on modern computers, which corresponds to Advanced Configuration and Power Interface or ACPI Mode S3.

While the desktop computers go into sleep mode after a set period of inactivity, the laptop computers can also enter into this mode when you close the screen or lid.

Sleep mode is also known by different names, such as:

  • Standby mode
  • Suspend mode
  • Suspend to RAM

When in the sleep mode, all the power-hungry components of the computer system are shut down, such as:

However, in this specific mode, the Random Access Memory or RAM is refreshed continually so that all the necessary contents are retained and you can start working right away from where you left off.

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The CPU, which was throttled down in the sleep mode to the lowest power state, is restored immediately.

Therefore, the computer starts working right away from its sleep mode when any of the following actions are performed:

  • The mouse is moved
  • Any key on the keyboard is pressed
  • Pressing the power button
  • Opening the lid of the laptop

It can also wake up when a signal is received in the Local Area Network or LAN or there is an incoming phone call on the modem.

When you do so, you will typically find yourself at the same point as when you left, with the same files and applications that you were working on open.

Hybrid Sleep Mode

Depending on the design and the model of the computer system, it may also support a specific type of sleep mode called the Hybrid Sleep Mode. This is actually the combination of two different types of regular power-saving modes, such as:

  • Sleep mode
  • Hibernation mode

This specific mode works in a bit different way, as follows:

  • First, all the contents of the memory are copied to a non-volatile storage for hibernation.
  • Then the PC enters sleep mode, rather than powering down.

This means that in this particular mode, you can enjoy the benefits of both. This specific approach is better than regular sleep mode due to two specific reasons:

  • The system can start working instantly.
  • You can also power down the computer system completely without worrying about losing your data.

OS Support

All operating systems from Microsoft Windows 2000 and later support this mode at the OS level and do not need any specific type of hardware or drivers for it, apart from the video adapters.

As for macOS, it supports two types of sleep modes, such as:

  • Safe Sleep
  • Power Nap

It typically does not support the Hibernate option because, unlike other operating systems, the Safe Sleep mode also allows restoring the state in the event of a power outage.

Is it Better to Sleep or Shut Down the PC?

Well, in simple words, based on the time factor, it can be said that sleep mode is better to use for a short period of time, during a coffee break, for instance.

On the other hand, normal shutdown and startup are better options to go with for longer periods of non-usage, such as going out for lunch or some work, retiring for the day and using it again in the next morning, and others.

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Though both of them are quite good energy-saving options, this is not an easy question to answer or decide which among the two is a better option because there are a lot of other factors, apart from time, to consider.

However, the following points may help you make a decision for yourself.

Usually, the sleep mode parks the hard disk and shuts down the display to prevent damage.

In comparison, normal shutdown and startup, on the other hand, allow the system to:

  • Clear the memory out.
  • Perform different self-tests.
  • Send you an alert for minor errors.
  • Inform you about software updates.

However, if you shut down your PC, it will take some time to restart your computer system and start working again, which, however, is not the case with sleep mode.

Please be informed that even putting your computer in sleep mode for a long time may also cause it to shut down abruptly because it will still draw quite some power to retain the required data.

Therefore, it is safe to say that it all depends on your time of usage. If you use your system for a long time and take breaks off and on, it is better to use the sleep mode. Otherwise, it is best to shut down your PC.

Therefore, go for sleep mode if:

  • You use your system as a server.
  • You want to access your PC remotely.
  • You do not want to miss out on the virus scans, background updates, or other activities.
  • You do not want to wait for your system to boot up or start up.

On the other hand, go for a complete shutdown if:

  • You care about energy waste.
  • You do not want an increase in your monthly energy bills.
  • You do not want those disturbing notifications.
  • The fan noise is annoying you.
  • You know that rebooting will improve the general performance of your system.

Is Sleep Mode a Security Risk?

Simply put, a computer system put in sleep mode typically should not be considered a secure option. In fact, it is a vulnerable mode because, in the event of a power drop or surge, a system that is powered by an adapter can be harmed more when it is in sleep mode rather than shutting it down completely.

Therefore, there is a high possibility of data loss since the necessary information along with sensitive ones and encryption keys are all retained in the RAM.

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Also, if you stay away from your PC for a longer time, sleep mode is not a safe option because your system can still be hacked in sleep mode, a possibility that is eliminated when you shut down your system.

Then there is the heat factor to consider. Typically, when you put your computer system in sleep mode, the internal components will still be exposed to a considerable amount of heat most of the time, thereby affecting its life and normal functionality.

Therefore, if you keep your system in sleep mode for a longer period of time, the life expectancy of the components will be reduced by a significant margin.

This risk is even more profound for older computers since they have older components.


  • It uses little power and therefore saves energy.
  • It reduces monthly energy bills.
  • The system starts up faster since it does not need to reboot.
  • You are back at the same point where you left off some time ago.
  • You do not have to reissue any instructions.


  • It still uses some amount of energy.
  • The RAM can never rest and therefore may become overloaded.
  • It may take a long time to go to sleep if there are more applications running.
  • It is vulnerable to damage and failures due to power drops or spikes.
  • Data can still be hacked into a PC that is in sleep mode.

Questions & Answers:

Is It OK to Leave a PC in Sleep Mode All Night?

Simply put, no, it is not. Typically, considering the recommendations of the U.S. Department of Energy, it is better to use the sleep mode if you are not going to be away from it for more than twenty minutes.

What is the Shortcut Key of Sleep?

You can use the Alt and F4 keys on your keyboard to enter sleep mode.


So, with all that said, now you know that the sleep mode, whether hybrid or regular, is quite a useful feature that modern computer systems typically come with.

It saves a lot of energy and even enhances the life of the parts inside the PC. However, there are still some risks involved. So, use this feature judiciously.

About Dominic Cooper

Dominic CooperDominic Cooper, a TTU graduate is a computer hardware expert. His only passion is to find out the nitty gritty of all computers since childhood. He has over 12 years of experience in writing, computer testing, and research. He is not very fond of social media. Follow Him at Linkedin