(I am sure I had notes on low power?)
There is lots of things you can do to lower power. Normal power on my Arduino Mega is about 50mA. And I have had it as low as 0.8 mA (800uA). And I have been told that is 600uA of just Regulator quiescent current loss. Quite a variety.
Special hardware and software you can get down to < 2uA !
- The Power LED was taking 2 to 3 mA
Software - AVR Power
Software - Sleep
Checkout Rocket Scream library. Not only great little library, but really nice people. http://www.rocketscream.com/blog/2011/07/04/lightweight-low-power-arduino-library/
Problem - Serial.begin
Just doing a Serial.begin on one of my devices lifts my sleep current from <1mA to 18mA... yet Serial.end(), or even setting the pins as output, low don't seem to work.