to check on my power consumption. The nice thing about it is you can plug in individual miners or a few if they go into one plug and you can check how things change if you swap out older less-efficient power sources for newer, more efficient PSU's. Trying to figure out what the power draw is on a miner based on how your PSU is supposed to perform isn't a terrible idea but this takes the guess work out. It's proved really useful to me to insure than I am not overloading individual plugs of circuits in the house. Its also generally useful around the house to see what various appliances use. i.e. How much extra power do you use when you turn your window air conditioner from low to high, etc...