There's no change in the power consumption of those drives if you have them disabled in software or not.
I have 5 hard drives in my system, but, at most only C and D (2 drives) really need to be enabled, so what I do is disable the other 3 by right click on the drive, select the appropriate drive and in the properties tag, select DISABLE THIS HARDWARE.
When required, just enable it.
Question is, when disabled, is power actually removed off that hard drive, or is there a quiescent current (small current) still flowing in the electronics of the drive that is disabled ??
Many thanks in advance.