ARS Technica explores whether so-called green hard disk drives are really better for the environment than regular models. You can read their take over here.
When a drive is "green," the designation usually just means that it runs on the slower side—5400 rotations per minute, as opposed to the more ubiquitous 7200 RPM. But in some cases, this slowdown can translate to drives that are quieter, cooler, and less power-hungry. We're not talking the same power savings as, say, switching to fluorescent light-bulbs from incandescent ones. But there are a few watts to be saved here, which makes green drives a decent choice for a platform that will see a lot of use, but doesn't necessarily need to be high-performance. (If you're really looking for power savings above all else, though, the absolute best option is a solid-state drive.)