First I must declare a vested interest here. David has promised to buy me a vest if I mention his software.
Actually no. In the old days only my mother bought my vests. Now number one wife does it.
But I work with David, which is how come I can recommend things he makes. Like Powerdown. You can get it here. It turns your computer off when you aren't using it. And makes it come back on quickly when you need it again. It is particularly interesting for large companies, who might have hundreds, perhaps thousands, of machines which they would like to make greener.
Powerdown also provides a way of controlling the power characteristics of large networks of computers from a single point, properly integrating with corporate systems to make things easy to manage.
Well worth a try.