This is one of the most common questions I get, and its not surprising considering how many factors are involved.

Factors:

• One of the very common things that causes electronic devices to fail is cracks that develop in connections on circuit boards. Often these develop after repeated heating and cooling cycles, that is to say. When you turn on the device it heats up and the hot parts expand, when you turn it off everything cools down and shrinks, The heating and cooling can cause cracks to develop over time. This is most likely the source of the leave it on all the time argument.
• You may need to leave your computer on if you need to access your computer over a network for file or printer sharing, if you want to schedule maintenance like disk defragmentation, backup, or antivirus scans.
• Components with moving parts like fans (your computer could have 3 or more) and hard drives tend to wear out faster if they are run continuously.
• Your computer may be using as much as 100 watts while it is on but idle. That could be over 2 kilowatt hours per day of electricity, at BCs low electricity rates that could be 16 cents per day or almost $60 per year.

In the end, how you use your computer will be the real determining factor:

• If you use your computer only during the work day, or only a few hours per day, you should probably turn it off when you are finished for the day.
• If you use the computer on an off during the day and evening, you may want to leave it on all the time.

Options:

• Turn it off but have it turn on automatically so you don't have to wait for it to boot.
  Most computers have power management options in the BIOS setup program to wake the computer at a pre-determined time each day, so you could have your system programmed to wake up 15 minutes or so before you expect to want to use it so that it is booted and ready when you need it.
• Hibernation - Windows offers an option to write the system state to a file on the hard drive and then shut down, When you turn the system on again, it loads this file and picks up exactly where you were when you put it into hibernation. This is usually faster than a normal boot up and allows you to resume working where you left off, even if its in the middle of a game of solitaire.
• S3 Sleep or Standby - Probably the most desirable option for an idle computer. S3 standby that turns off most of the system components (making the system silent), leaving the mouse, keyboard and RAM memory powered on to save what you were doing and allow you to wake up the system with the keyboard, mouse or power button.
• S1 Sleep or Standby - This option turns off parts of the computer and leaves other parts on, S1 standby leaves the power supply and other fans on but turns off the display and hard drives and allows you to wake up the system with the keyboard, mouse or power button.
• If your system uses S1 standby, in some cases you can force S3 standby mode in the Power Options menu of the BIOS setup program. It may also help to install the newest BIOS and driver software available for your computer (downloaded from the manufacturer's website.)

Limitations:

• If you are using Windows 95, 98 or ME the power management is not very reliable, you're lucky if your computer turns off properly by now, its time to upgrade (for so many reasons.)
• Many computers (especially older ones) have problems with sleep mode, either they don't wake up properly or they go into S1 not S3 standby so they use more power and make noise. Try to locate the newest available BIOS firmware on the main board manufacturer's website, and check for driver updates that may also be available.
• If your system hangs waking up from standby, or just seems to hang when you are away from it, it may be that the hard drive is not spinning up correctly from its low power standby mode, its quite common for older drives to develop this problem even if they worked in fine previously, your options are replace the drive or disable the hard drive power down.