A reader from Canada e-mailed us and asked, "Would you give me your opinion about leaving the computer on during the day, unless there is a storm on the horizon?" We get this question quite often.
The rule I use is, if I am going away from my computer for about an hour or less, I leave my computer turned on. If I am going away for about an hour or more, I turn it off.
When I leave the computer turned on, I usually turn the screen off (the screen uses a lot more power than the computer, so this saves quite a lot of power).
It is possible to set most computers so they will turn their screen off after a certain amount of time with no activity on the keyboard or mouse, but I dont use these "power saving" features, because they have (in the recent past) tended to cause some problems with some programs.
If you turn the screen off, just remember to ONLY turn the screen switch on, NOT the computer's main power switch (i.e. if you forget the computer is not off, and you hit the computer's power switch, the computer will go off, which is not good for your computer).
Rationale: The reason I turn the computer off when I'm not using it for a while, is that (1) it uses power when it is on, (2) the hard drive and the fans spin when the computer is on, and these wear out (we also sell computers and repairs in our business, and we have often seen this). The reason I leave it on if I'm just going away for less than an hour, is that (1) turning it off and on a lot causes more wear on the circuits and the hard drive, (2) it takes less time to turn the screen on, than to start the computer, and (3) if I leave the file I am working on open, I don't have to open it when I get back, which saves more time.
NOTE: If there is an electrical storm, I prefer to have my computer OFF, because computers are somewhat sensitive to electrical variations.