teckel:
If the Due is anything like the Uno, it will use quite a bit doing absolutely nothing. The Uno doing noting at 16 MHz uses 61 mA with an 8 volt source. From there add whatever else you'll be running.
True, but it can be forced to idle at much lower current a few different ways. I wondered the same about the UNO not too long ago and was pointed towards this page: http://www.gammon.com.au/forum/?id=11497
However, if the OP is looking to keep the current draw low while operating his program that's a different story.