Put your PC to sleep when it is idle

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We don't use our PCs all the time. We take coffee breaks, we take lunch breaks, we go and watch our favourite TV programme or sports team. There are times od the day when your PC is idle and it is not doing any work at all. Apart, that is, from consuming lots of electricity and generating lots of heat - have you felt how warm PCs get? This is not good for the environment because electricity generation causes greenhouse gasses and it is not good for your bank balance because it will increase your bills.

You should put your PC to sleep or into hibernation when it is not being used. Sleep mode is a reduced power state that keeps all your programs running, windows and documents open, but uses very little electricity. Tap the spacebar or shake the mouse and the computer will instantly burst into life and you can carry on where you left off.

To set this up, go to the Control Panel and open Power Options. In Windows 7 you get a choice of Balanced, High Performance and Power Saver. The last one, Power Saver is a good choice if you are running a laptop computer on the battery, but for desktop computers you should select Balanced.

Click the link, Change plan settings. There are two timers and the screen display is set to turn off after five minutes inactivity. The computer is set to go into sleep mode after 10 minutes inactivity. If you find that these settings are too short or too long, you can change the time from the drop-down lists.

Click Change advanced power settings. Expand Hard disk, Turn off hard disk after. The default time is 20 minutes, but clicking the time lets you change it. You might want to change the timer to 15 minutes for example, because this would save more power than the default 20 minutes. It takes time to spin the disk back up to speed, so you don't want the timeout to be too short or the PC will turn off the disk if you answer the phone or spend a minute in deep thought. About 15 minutes is the shortest time that is convenient.

Expand Wireless Adapter Settings then Power saving mode. Click the setting and you can choose from low, medium or maximum power saving, or maximum performance. It's mostly laptops that have wireless internet connections, and one of the three power saving modes should be selected to make the most of the battery. If your desktop PC doesn't have wireless capabilities then ignore this setting.

Sleep, hybernate and hybrid sleep
Expand the Sleep section and you will see Sleep after, Allow hybrid sleep, and Hybernate after. What are these? In sleep mode the computer stops what it is doing and this reduces its power requirements. When the computer hybernates it saves all your programs, windows and documents to disk and then powers off the computer completely. It saves the most electricity and is the most environmentally friendly, but it can take some time to power up the computer when you want to use it. This is OK if you are switching off at night, but the delay can be irritating if you have just paused to answer the phone.

Hybrid sleep is the best option and it should be set to on. It's a sort of half sleep, half hibernation. The computer pauses all activity as in sleep mode, but your programs, windows and documents are saved to disk like hibernation. They are also kept in the PC's memory too. The power is reduced to a minimum, but it is not quite turned off. The advantages are low power consumption, but fast starting when you want to get back to work because everything is still in memory. It is the best option for desktop computers.

My computer won't sleep or hibernate
If all the modes are enabled, but Windows won't automatically put itself into low power hybrid sleep or hibernation after a period of inactivity, it is probably because of a program running in the background or a device that is preventing it. USB and bluetooth devices can both prevent a PC from hybrid sleeping or hibernating. There may be a setting in the software for the device that enables or disables its ability to wake the PC.

There isn't an easy way to find out what is preventing standby and you should eliminate possibilities one by one. Use Windows Update to make sure you have all the latest bug fixes and service packs. Then look for driver and software updates for the video card, printer, scanner, wireless mouse or whatever hardware you use. Unplug devices that aren't actually being used, such as a scanner. Uninstalling any software that you don't need.