The computer lab in the Faculty of Science, NARGA, has 4 classrooms and 2 open areas containing a total of 310 computers. Of the 6 rooms, 4 are available 24 hours a day. Obviously not all the computers are in use all of the time. We have implemented an auto-shutdown policy that applies in the event that a computer becomes idle after hours. This policy has been active since the beginning of 2008.
The script runs every 30 minutes from 16:00 every week day until 04:00 the next morning. It also runs every 30 minutes all weekend. The schedule is set via Group Policy Prefences, a new tool made available by Microsoft with Windows Server 2008. When run, the script checks for an active login. If none is found, the script checks twice more at 5 minute intervals. If no active login was detected by the three checks, the assumption is made that the computer has been idle for more than 10 minutes, and may be shutdown. The tools used are psloggedon and psshutdown by Mark Russinovich of www.sysinternals.com.
During the semester, all the computers are woken up 30 minutes before the first classes start to have them ready when the first students arrive. During exam times and holidays, no auto-wake is performed. The auto-wake is implemented by way of sending a Wake-on-LAN magic packet to the lab.
We estimate that roughly 90% of our computers are shut down for at least 6 hours every night, with at least 40% shut down for more than 10 hours.