With Windows power plans, it's really easy to let the computer itself determine how to optimally use power based on what you're doing. But if you know for certain that you don't need a particular background process, you can disable it. It only takes a few seconds to open it again when you actually need it, so it's hardly a big inconvenience. That's all well and good when you're actually using it, but what about all those breaks you take from it? That aside, obviously, lowering the supplied voltage to these components lowers the total amount of power the PC is using.