I did some napkin math on the overall effect of the new version of Mavericks, and wanted to share. Standard caveats apply: as you’ll see, I’m doing a lot of hand-waving.

Starting assumptions:

• Adoption of Mavericks will equal Mountain Lion* for ~30 million users
• 75% of Mac sales are laptops
• I’m using the Mac Mini for desktop power consumption to concentrate on processing/disk tasks
• I’m also using it for the under-load draw for laptops

So! Thirty million Macs, idling, draw 195 megawatts. Under load, they draw 2,380 MW.

Assume Mavericks gets you a 15% savings in power both at idle and under load.*** If all Macs are at idle, you’re saving 30MW. If all the Macs are running at the same time, you’re saving 357MW.

How much is that?

• The smallest nuclear reactor in the US generates 438 megawatts
• An average coal plant generates about 500 megawatts

Now, you don’t of course get all the savings at once, and I’m totally omitting how Mavericks affects machines staying in minimal power draw states longer instead of waking, working, sleeping, waking…

I welcome thoughts on how to improve my napkin math and get to a better number.

Even as a rough guess, 80% of a coal plant… that’s pretty awesome.

* I assume this will be low, as new Macs will come with Mavericks installed and replace ones that don’t, and also because with power-saving features, there’s a huge incentive for laptop users to upgrade if they are able but haven’t. Also, it’s free.
* nuke cite http://www.eia.gov/tools/faqs/faq.cfm?id=104&t=3
*** I’m guessing, based on anecdotal reports of battery life improvements, mostly during betas