Apple's Snow Leopard upgrade to OS X has many subtle behind the scenes powers that assure it'll remain cutting edge for a good while, but it also seems to have unexpected green skills: It could save the world 50GigaWatts of power.

The issue is getting some discussion over at ComputerWorld, based on an experiment CNET did with a MacBook Pro 17-inch running both OS X 10.6 Snow Leopard and the older Leopard 10.5.6 installation. Check out the table to see the math in all its simple glory:

How can an OS upgrade save electrical power? It's subtle but simple: OS X Snow Leopard is just more efficient, and not in a CPU calculations-per-second basis--that's all hard-wired into the microelectronics. It's in terms of time to start-up and turn off a Mac running the new OS, wake-on-LAN powers which let a Mac idle and spin down its hard disks when you're not accessing it over a network and in the way the Grand Central code more efficiently manages a multi-core processor to get maximum value out of a compute cycle. Each tiny efficiency means a machines hard drives are spinning less and the machine is actually consuming power for a tiny amount less time.

Added up, Snow Leopard's efficiency savings equate to around a dollar less electricity consumed over a year of use, by CNET's maths. And that's nothing--but with so many millions of Macs out there, and with Snow Leopard expected to sell five million units in this quarter alone, the savings quickly multiply up to millions of dollars and gigawatts of electrical power.

Will we see Windows 7 delivering similar green savings when it launches next month? I suspect not--and even if there were any, they're probably overridden by the ridiculously voluminous eco-unfriendly plastic packaging that Microsoft has chosen. Apple really can say it's turning green.

[CNET via ComputerWorld]