retrolefty:
An arduino board is based on a AVR microcontroller chip and when the board with nothing wired or attached to it consumes around 80ma of 5 volt current, and that includes the 8U2 USB chip, the power on led, and other components on the board.
A while back, I measured an Uno (but not an R3) at 42mA. I wasn't aware if there were changes with the R3 that might have increased that significantly. Just curious.