Western Digital Caviar GP 1 TB (WD10EACS) is a 1 Terabyte SATA 3 GB/s hard drive. Model # WD10EACS is available in 3 capacities: 1 TB ($250), 750 GB ($230) and 500 GB ($130). The "GP" is an acronym for "GreenPower", aka Caviar Green. WD Caviar Green drives reduce drive power consumption by up to 40%, with power savings around 4-5 Watts over traditional hard drives. The manufacturer claims that the equivalent reduction in CO2 emissions would be if you took a single car off the road for 3 days a year.
