Another thing to think about when using sleep is that if the power goes out (and you don't have a UPS) you will loose any unsaved data since the data is stored in the memory.
Hibernation is the better alternative if you don't have a UPS since everything is saved to the HDD (and it also uses less power, same amount as when the computer is "off"). The only thing is it does take a little longer to come out of hibernation than sleep (but is still quicker than a cold restart).
Originally Posted by Nebacanezer
If your system is overclocked and is a high end system I would say turn it off when you are not using it. Some argue that the wear and tear of sleep is not worth the benefit. However, if it is your everyday computer that you use for school/net browsing then just put it to sleep.
I have always put my work computer to sleep and shut my gaming rig off when not using it or if I am going to be away from it for over an hour. The amount of money you save by shutting the computer down vs. letting it sleep is pennies on the dollar. And if your parents are that worried about the bill, unplug the computer when it's off because it still uses electricity when plugged into the wall.
What "wear and tear" does sleep cause?