For the new Unity 7 low graphics mode, Ubuntu will soon made it easy to enable or disable this feature using unity-control-center (System Settings -> Appearance -> Behavior).
The desktop team improved the Unity 7 low graphics mode a few months ago by reducing the amount of visual effects that are seen while running in low gfx. Now a toggle option for the new (fast) low gfx will be land in System Settings soon:
However, for those still have the old lower-performance lowgfx, the option will be grayed out, the developer explained in his blog post:
If you can’t select “Switch to low graphics mode” it means that you still have the old lower-performance lowgfx and you can only switch to it from ccsm->unityshell->low gfx, if you are able to select it, you just check/uncheck the button to enable/disable the new features and don’t need to use ccsm at all. 🙂