A question I got at work ...

What takes more [energy]?

A current iMac with the display off or a 4 year old mac mini with no display?

When you say “display off,” I assume you have forced it not to sleep, despite the current iMac’s sleep proxy built into the Ethernet chip. i.e. it acts like it is awake even if it is asleep. And no external sleep proxy (like Airport Base Station) already running to handle letting the mini sleep.

I also assume you already have (or will have) both systems and aren’t considering purchasing a new iMac to replace the mini. The new iMac has more physically “embodied energy” when it arrives at your door (before you even turn it on) than the mini you already have consumes in both manufacturing and typical (not 24x7 idle) customer use.

According to <http://www.apple.com/environment/reports/>:

- a 2013 iMac 21” idles at ~14.5W and sleeps at 1.25W

- a 2013 iMac 27” idles at 20.5W and sleeps at 1.03W

- a 2010 mac mini (is that what you have) idles at 9W and sleeps at 1.39W

It looks like the mini is the winner if you are going to leave it running while the 27” iMac *might* be the winner if it was asleep: I assume that sleep power goes up when you plug in Ethernet.

If the mini can do the job, let it, and consider using Wake on Demand.

-Soren