Just for fun, here are some power consumption figures (based on data from storagereview.com%): Idle power draw (3.5in drives): around 5W Load power draw (3

Just for fun, here are some power consumption figures (based on data from storagereview.com%): Idle power draw (3.5in drives): around 5W Load power draw (3.5in drives): around 6.5W Spinup power draw (3.5in drives): around 15W Idle power draw (Samsung 2.5in): 0.58W Load power draw (Samsung 2.5in): 2.53W Spinup power draw (Samsung 2.5in): 3.89W Of course spun-down (as opposed to idling but spinning) HDDs draw far less power. I found a 2008 report# which measured spun down power, and it ranges widely but 10 to 20% of idle seems to be about right. (Not sure if there's a 2.5in drive among those they tested; I only skimmed the report.) If you disregard the spun-down thing for a moment, you get about 4W savings all the time, ie. 20W for the full array. That's about 175 kWh over a year. Assuming 0.20 EUR/kWh (which seems fairly typical for Germany), that's 35 EUR you save, per year. I guess that number can serve as an upper bound for the savings you can expect, chances are it'll be much lower: not a full array, 50% or more time spent spun-down, your energy prices might be lower. % http://www.storagereview.com/samsung_spinpoint_m8_review http://www.storagereview.com/samsung_spinpoint_m8_review http://www.storagereview.com/western_digital_caviar_green_2tb_review_wd20ears http://www.storagereview.com/western_digital_caviar_green_2t... # http://www.cl.cam.ac.uk/~acr31/pubs/hylick-harddrive2.pdf http://www.cl.cam.ac.uk/~acr31/pubs/hylick-harddrive2.pdf