Disk Power Consumption Calculator

Drive power consumption has three states: idle, read/write and full load. For typical models: a 3.5-inch HDD idles at about 2-4W, reads/writes at 4-8W and peaks at 6-10W; 2.5-inch HDDs and SSDs are much lower, with SSDs idling at about 0.5-2W and reading/writing at 2-5W. Actual draw also depends on model, capacity and spindle speed — this calculator gives a planning estimate.

Take one 8TB HDD: 3W idle and 6W read/write, idle 20 hours and read/write 4 hours per day. At a typical rate the drive uses roughly 30.7 kWh per year. A 4-bay NAS would be about four times that. Low-power drives or SSDs reduce it noticeably. Substitute your local electricity price for an exact figure.

An SSD typically draws 30-50% of what an HDD of the same capacity does. In a typical setup an HDD idles at 3W and reads/writes at 6W, while an SSD idles at 1W and reads/writes at 3W. Running 24/7, one HDD uses roughly 35 kWh a year against about 15 kWh for an SSD. SSDs are also silent and faster at random I/O.

Common ways to cut NAS power draw: 1) choose low-power drives — 5400 rpm models typically use 20-30% less than 7200 rpm; 2) enable drive hibernation, which can drop idle draw below 1W; 3) use an SSD cache for hot data so HDDs wake less often; 4) right-size the array instead of keeping many drives spinning for little data; 5) turn off services and schedules you do not use.