Snow Leopard saves millions of kilowatt hours of electricity?

Of all of the numerous improvements in Snow Leopard, the biggest might be its miserly use of energy. Snow Leopard doesn't just speed up your Mac; it also makes it a better environmental citizen.

Apple already had good energy saving credentials before Snow Leopard was released, including Energy Star ratings for all of its computers.

After installing Snow Leopard, many have found their battery drain rates had decreased, indicating a lower power draw. I get about 10-20 additional minutes out of my MacBook Pro since upgrading.

I'm not certain where all of the energy saving takes place, but Grand Central Dispatch could certainly manage processors more effectively, thereby saving some CPU cycles.

CNET got some hard results by testing a 17-inch MacBook Pro with Leopard and again with Snow Leopard and found that using Snow Leopard would save 10 KWh of energy per year. Sure, that is only around a dollar of savings — ut Apple is upgrading a lot of Macs.

Table from CNET:

Apple is expected to sell at least five million copies of Snow Leopard this quarter. That's where the economics of scale start to make a huge impact. If every machine saves 10 kWh of energy and $1 off the electric bill, that comes out to $5 million in saved electric bills and 50 gigawatts of electricity. That's enough to power a flux capacitor!

It isn't just regular operations in which Snow Leopard saves electricity. Snow Leopard uses additional refinements to save even more energy:

— Time Machine backups are up to 80% faster. That means less disk spinning on both your boot disk and the backup drive. Also, Snow Leopard takes up much less disk space, meaning there is less data to back up.

— Wake-on-LAN allows Macs to sleep between file sharing sessions, which allows machines to be be effectively off when waiting to share. Previously, you'd have to leave you Mac running if you wanted to share files.

— Boot Camp now has better sharing options, allowing fewer restarts to get data from one OS to the next.

— Startup and shut down both now take half the time as Leopard. You are saving time with the computer on — and time is energy.

(from apple.com)

— Overall efficiencies. Snow Leopard is riddled with refinements that make workflows more efficient. The more quickly you can do your work, the less time you spend on your machine using energy.

While it may not be its biggest selling point and might only save its customers a buck per year, Snow Leopard's power-saving capabilities certainly should impress those who care about the environment and their carbon footprint.