ZeroPlan is a simple app that switches the power plan from “High Performance” to “Power Saver” when you unplug your PC, and vice versa.
It has no installer, no GUI, no options, and uses only a little more than 1 MB of your RAM. Just stick it in your Autorun folder, and you’re ready to go.
It uses Net Framework 4.5, so in theory it should be able to run on jailbroken Windows RT devices.
Download Source (GPL2)