The problem domain isn't "monitoring plants with only an AA battery for power" though. It's a host capable of running Linux and assorted toolchains for embedded software development. I know that there are systems for all kinds of applications and the power envelopes they prescribe. That's not the issue. The issue is that someone proclaimed that "electricity is expensive. Douche bag." And that's not true. Electricity is cheap. Cheaper than hardware which is incredibly cheap itself. And that holds true even for the very low end, where a tiny amount of energy is sold in an expensive package, but a finished system will still cost more than the batteries it takes to run it for a couple of years before it is replaced, yet the hardware is sold at prices which almost make the devices disposable. For perspective: How many smartphones does the average person buy per year? Still think a low to mid range quad core desktop system is expensive?
So I do development and I want to cut my costs down. I presently have a desktop at home with a 600W supply and a server with a 250W supply, as well as laptops with 60-90W supplies. As I use the desktop for other things (e.g playing DVDs, Netflix, etc.) I'm satisfied to leave it for now; laptops might get replaced by tablets or chromebooks.
But the server? I keep it on a UPS, and would love to be able to keep it up for a very long time. On the UPS it would only get between 10-30 minutes if power fails (APC 1500). I am very interested in switching it out for a few lower power devices. In fact, I'm targetting replacing it with 3 devices (a Rasberry Pi for authentication, a Udoo for disk storage, and a Routerboard for firewall support) with a total power envelope of 50W.
Do I still intend to do software development on the server? Yes.
Do I still intend to do DNS, DHCP, Samba, WebServers, etc on the server? Yes.
But you know what - unless I'm building something targetting a mainframe, some heavy video driven application (e.g games, autocad, etc) then I really don't need a very powerful system. Point being - a beagleboard, Udoo, or Rasberry Pi really is sufficient for most people doing software development....well, unless you're trying to use Eclipse or Visual Studios, but then you're just asking for trouble.