Recent 7200rpm notebook drives are 0.8W idle; very low and comparable to 5400rpm. Check the specs for the disk you want to buy, the newer the better. The older 7200rpm disks can go well over 1W idle power consumption; at around 2W you're in the danger zone of the HDD being capable of destroying itself via heat buildup. 2W is alot of heat on a tiny surface if it has no way to escape or dissipate.