Most computer users (including me!) find it inconvenient to remember to put their computer to sleep when they're done using it for the day (in order to conserve power). As a result, it rarely happens. In an office environment (with 9:00a - 5:00p work hours), that means that a single computer sits idle for about 12 hours a day (80 hours during weekdays), plus 48 hours over a weekend. That's 128 hours in a week that only has 168 to begin with (or 76% of the week). That's a lot of power wasted! And when you consider the number of computers in your organization, that can have a real impact on your financial bottom line.
Mac OS X has a really great energy-saving feature that solves this problem for you. It allows you to either put your Mac to sleep, or shut it down completely on a set schedule. It also allows you to wake your Mac up on a schedule. Combining the two would mean that you leave the office with the computer on, and return to the office with it still on. The only difference is that the computer went to sleep while you were away, with no human interaction.
To enable this feature, open System Preferences, then click on the Energy Saver button. From here, click on the "Schedule..." button in the lower right-hand corner to expose the following options:
The settings are pretty self-explanatory, so I won't go into unnecessary detail. I will, however, make one cautionary note: if you decide to shut the computer down (as opposed to put it to sleep), you won't be able to start the computer again automatically. Unfortunately, this isn't very clear on this screen.
In order for these settings to work, your computer needs to be turned on (obviously) and you need to be logged in to your account. If you have a screensaver that kicks in, these features will appear not to work at the exact time you set it to go to sleep or shut down. However, if you wait the 10-minute time-out period (which you won't see if the screensaver is on), you will find that will eventually shut down or go to sleep as designed. This is what the time-out window looks like:
My recommendation is to set your Mac to go to sleep at a time that makes sense to your work schedule, set a time for it to wake up that also makes sense with your work schedule, automatically have your screensaver turn on after a couple minutes of no activity, and require your password to disable the screensaver. This 1) conserves power, 2) ensures security and 3) completely automates the process.