The 100mW active power rating for the 660p is almost certainly measured while running MobileMark, a general system performance benchmark that is very lightweigh

The 100mW active power rating for the 660p is almost certainly measured while running MobileMark, a general system performance benchmark that is very lightweight and leaves the storage completely idle for the bulk of the test duration. So that power rating is really more of an indicator about idle power in a machine sitting at the desktop doing nothing (but not in a suspend/sleep state at the system level). The 990 Pro power rating and the enterprise SSD power rating are both for a drive that's actually busy. The Micron 9400 has a controller with twice as many channels and none of the performance-sacrificing optimizations that consumer SSD firmware comes with.