Power-saving modes for your computer–how to use them to best advantage

An issue that can be of concern with computer users is choosing the best way your computer should behave when it is in an idle or dormant state.

Since Windows 95 and the arrival of the ATX chassis with the software-controlled power supply, it has become more feasible to provide software control over a computer’s power needs. Macintosh users have had this ability all along and this was gradually implemented in to Windows laptop computers just before 1994.

Now there are a range of software-controlled reduced-power modes that a computer can be set to assume when you are not using it. The different modes work in order to make sure that work-in-progress data isn’t lost and that the computer “knows where it is” when it comes to.

Power conditions

Peripheral sleep

This mode is a common idle-operating mode for computers not actually doing something and is often set up by default. This is where hard-disks or other mechanical drives spin down and the the display turns off, but power is maintained to the RAM, system processor and communications circuitry.

The computer then operates at full steam when you operate the keyboard or mouse or, in some cases, connect peripherals or insert removable media.

System sleep / standby

A computer that operates in this mode has the processor and RAM and, in some cases, certain communications channels consuming power but the processor is operating under a low power condition. This mode then allows for instant-on wakeup when you need the computer. This power state is typically indicated with the power light slowly flashing  or changing to a colour like amber.

Then it may be woken up by, in some cases, you using a keyboard or mouse or just pressiong the power-control button.

Some Windows 7 and newer Macintosh laptop computers implement a “hybrid sleep” where the contents of the RAM are dumped to the hard disk / solid-state drive when they enter this mode. This allows for the battery to die down without loss of data.

Hibernate / Deep sleep

When a computer is placed in the hibernate or deep-sleep mode, the current contents of the RAM are dumped to a special file on the computer’s hard disk or solid-state drive. Then the computer shuts off completely.

The tradeoff with this mode is that it takes slightly longer for the computer to be at useable state due to reading from the hard disk. For SSD-based systems like netbooks, Ultrabooks and the Toshiba R830 that I reviewed previously, the restore time would be likely to be short compared to a hard-disk-based system.

When you need the computer, you just activate the power switch where the computer will start up and read back the data from the secondary non-volatile storage.

All Windows laptops have supported this power state “out of the box” but MacOS X computers require the user to download and install third-party utilities to implement this mode.

How can I best use these modes

If you are leaving your computer while it is transferring data or doing a long task, you could allow it to implement “peripheral sleep” for peripheral devices that aren’t relevant to the task. This can be done through setting up spin-down or display-off times using the power-control options in your operating system.

Implementing standby / system-sleep can be handy for computers connected to external power like desktops or laptops that are plugged in to their charger. But I wouldn’t recommend this for laptops running on their own battery, even Ultrabooks or other SSD-based power-optimised ultraportables.

I would implement the hibernate mode mainly as a preferred power-down mode on laptop computers. This works as a way of maximising battery availability especially if you want to have it available at the end of your journey. This is even though your journey may end up at your desk where you may plug the laptop in to power before using it.

The Hibernate mode is also more important for netbooks, Ultrabooks and similar units that you use as a secondary “traveller” computer and you may typically “lay them up” for a time period in an order of weeks or months as you stay working at your regular desk.

If you can, you may need to implement hibernate mode on your desktop if it doesn’t handle system sleep properly or is fed from an AC supply that is unreliable like in the country or peri-urban areas.

For laptops, it may be a good idea to check the power options to determine what closing the lid does when you set the computer up for the first time. This is more important when it comes to what it should do while on battery power.

It is also worth shutting down the computer and restarting it every few weeks, especially if you shift between networks a lot or connect and disconnect peripherals frequently.  The “boot” cycle that is part of the process gives the computer a chance to properly take stock of its storage, peripheral-device and connectivity environment.


Once you know what these low-power operating modes that your computer’s operating system offers are about, then you could be able to operate it in a power-efficient way especially when you are not using it and yet come back to a responsive machine.

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