Power Saving techniques

We are a school district in an energy saving mode. What is the best practice for a school to adopt to conserve power on hardware. We have instituted a practice of going to “standby” mode after one half hour to conserve. We are leary of machines being left on for days, etc. What is the cost savings? I am aware of an executable to provide shutdown to be pushed across the network at a specified time. Is this doable and will documents be saved, etc. Any history or ideas out there?