Dont go with the "apparent power" formula for the power or the stepper. As a large abstraction or just to compare ratings between motors maybe. But for actual standalone calculations, cant. Because the voltage is switched all the time, and you dont know how much is on/off so it would require some kind of average figure. The current we set is the peak value, where it gets interrupted, but peak is not an average either. Its worse, it has rising edges and just if we know whats the interruption point doesnt mean we know all the values to get there. It could get to that peak very fast or very slow, and results will differ by much. And even worse, the falling edges are nightmare in math terms as they can have synchronous rectification or output diodes and even some remainder of blank time, so the general shape of fall edge is not all that clear. So all this is just a bit too much to just make p = v*i and expect a result to mean something by itself.
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