I have the wattmeter, and the results are shown on an LCD screen in real time. Just hook it up between the battery and the ESC, and when you run the motor up, it will display 4 diff parameters. You can see what the set-up is actually drawing in terms of amps, or how much power, or watts your motor is putting out. Real simple to use honestly. No rocket science here. Get one...it makes fine tuning your setup a lot easier. You will be able to choose the prop that will keep your current draw within the batteries specs, and keep you from frying a motor basically