As others have said, the resolution on the B&D is not that great. But if you are really up for some tinkering, you could build something reasonably cheaply wit

As others have said, the resolution on the B&D is not that great. But if you are really up for some tinkering, you could build something reasonably cheaply with better resolution with A/C current sensors and an Arduino, like this guy: http://www.flashsense.com/?cat=3 http://www.flashsense.com/?cat=3