We tested the peak power consumption of a NAS at the wall during a run of CrystalDiskMark 5.0.2 as this version of the benchmark runs the read and write benchmark suites separately so its easier to monitor what power the device is using during each function.
Asustor quote operational power consumpton for the AS6404T at 24W (11.2W HDD Hibernation, 0.44W sleep). These figures were obtained testing with WD 3TB Reds which have power rating of 4.1W for active read/write and 2.7W when in idle. The WD 6TB Red drives we used for testing are a little more power hungry at 5.3W read/write and 3.4W idle.