The world's most powerful line of supercomputers - IBM's Blue Gene family - is by far the most energy-efficient, according to a new ranking of the TOP500 computers. The inaugural Green500 list ranks by energy efficiency the machines that make the overall TOP500 list of the world's fastest computers. The new Green500 list shows IBM Blue Gene supercomputers capturing 26 of the top 27 spots.

The Green500 list is overseen by two professors at Virginia Tech, Kirk Cameron and Wu Feng. "The Green500 List is intended to serve as a ranking of the most energy-efficient supercomputers in the world and as a complementary view to the Top500 List," Feng said in a press release.

IBM supercomputers also led on the recently-released TOP500 Supercomputer Sites list, which ranks the world's most powerful supercomputers. According to the TOP500 list, the IBM Blue Gene/L at Lawrence Livermore National Laboratory is the world's fastest supercomputer, capable of delivering a sustained performance of 478 trillion calculations per second (478 "teraflops"). IBM also placed a total of 232 supercomputers on the list, the most of any vendor.