Are “green” hard drives really all that green?

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.)

The three features that are touted the most often by manufacturers of green drives, as we said, are their relatively quiet and cool operation and their lower power consumption. These specs are measured in decibels, degrees Celsius, and watts, respectively, and can usually be found on fact sheets for various drive models on the manufacturer’s website (here’s a Western Digital sampling) or from third-party benchmarks, if you don’t trust Big Data Storage.

Some green hard drive models perform decently well in these areas over their desktop-standard counterparts. For example, a 1TB Western Digital Caviar Green model that runs at 3.0 Gb/s with a 32MB cache consumes an average of 4.8 watts when reading or writing, 2.82 watts when idle, and 0.38 watts when in standby or sleep mode. A WD Caviar Black with the same specs consumes 8.4 watts when reading or writing, 7.8 when idle, and 1 in standby or sleep. You’re not exactly slashing your electric bill with a green drive, but it’s something. You also drop a couple of decibels in loudness going from Black to Green.

Of course, what facilitates the difference between these two drives are their speeds— the Caviar Black runs at 7200 RPM, and the Green uses a mysterious system that WD calls IntelliPower. Theoretically, this is supposed to mean that it runs between 5400 and 7200 RPM depending on the demands being made, but most third-party tests have found the Caviar Greens pretty much stick to 5400 RPM.