If you want to know just how much energy your appliances are using, and exactly how much that energy is costing you, you need the Kill-A-Watt EZ, sold at ThinkGeek.

You can program the device with your exact energy cost (per kilowatt hour), plug in your device, and it will tell you exactly how much power is being drawn and what that power will cost over the course of a week, month, or year.