My basic question is: Which one does the power company bill you for?
Background: I have one of those "Kill A Watt" thingies, and I've noticed that it tells you the number of Watts, the number of "Volt Amps" (which is generally greater than Watts) and the "Power Factor" (which is, of course, Watts divided by VA, so it will be something like 0.6). I sort of, almost, understand the difference between Watts and VAs, but what I am really curious about is which one the power company uses to bill you. I would expect Watts, but you know how companies are, they usually pick whatever will maximize the bill...