The WD Green SSD is an entry-level product line with limited capacity options. Based on the SanDisk SSD Plus, it uses a Silicon Motion controller in a DRAM-less configuration with SanDisk 15nm TLC NAND. The WD Green has a similar purpose to drives like the Samsung 750 EVO and the recently-announced OCZ TL100: to offer the lowest possible price while still providing acceptable reliability and a noticeable performance jump over hard drives. Higher capacities are omitted from the product line because the total price would be too high for the most cost-sensitive consumers even if the price per GB is marginally lower than a more mainstream budget drive.
While the Green label has connotations of better than average power efficiency when applied to WD's hard drives, the low performance of DRAM-less SSDs usually leads to poor energy efficiency during active use and the idle power savings tend to be minimal.
The WD Green will be available later this quarter, and pricing has not been announced.