What grandparent commenter showed was the school district's numbers are plausible. I doubt the district entered into a legal battle without first consulting an engineer or two about the electric costs.
HP 6000 Pro SFF - Core2Duo E8400 @ 3GHz - 100% CPU: 70, Idle: 26, Sleep: 2-3, Off: 0-1,
HP 6200 Pro SFF - Core i5 3470 @ 3.2GHz - 100% CPU: 83, Idle: 31, Sleep: 2-3, Off: 0-1,
HP 6300 Pro SFF - Core i5 2400 @ 3.1GHz - 100% CPU: 100, Idle: 30, Sleep: 2-3, Off: 0-1,
It's been a few months now, and I can't remember what I used to max out the CPU. It wasn't SETI @ Home, but it should give you a pretty good approximation. When it was off, it had Wake on LAN enabled, so it still drew some power. But it would fluctuate between 0 and 1.