With the right combination of capacity, performance and rapid power cycling storage system designs can pump more iron while keeping cool and saving energy.
Storage device companies such as Seagate can provide cost effective storage solutions that could have special powersaving or performance features that would be attractive to open storage system designers.
Of course the total energy used by a hard disk drive depends upon the actual usage and powersaving modes, and caching of data can reduce the energy used by a HDD in a computer system.