Monitors consume a negligible amount of energy. Yes, you can get lower your energy consumption a little, but implementing what you guys have suggest may, at best, save someone a dollar a year on their bill. The processor using a ton of energy, followed by RAM, the GPU (the GPU can be first on this list), and then the HDDs. If you really want to save money, get energy efficient RAM, a low end GPU, and a ultra-efficient processor.