Alright, so back EMF is only affecting voltage, not current.
Agreed that for this estimate I probably would use the max motor rated current of 2A, rather than my expected current limit of 1.5A, so that gives 5.6W when stationary, what would be a reasonable multiplication factor to account for movement and back EMF? I'm not looking for an exact figure any more, when I first asked the question I expected to find a simple equation to say that a stepper will use x watts (peak) at a set voltage and current, clearly it's not as simple as that, so I'll be happy with just a ballpark figure with a reasonable safety margin built in.
Agreed that for this estimate I probably would use the max motor rated current of 2A, rather than my expected current limit of 1.5A, so that gives 5.6W when stationary, what would be a reasonable multiplication factor to account for movement and back EMF? I'm not looking for an exact figure any more, when I first asked the question I expected to find a simple equation to say that a stepper will use x watts (peak) at a set voltage and current, clearly it's not as simple as that, so I'll be happy with just a ballpark figure with a reasonable safety margin built in.