On the 175. Engine idle fuel burn is 500 lbs/hour and the APU burns 250/hour. In other words, 12.5 lbs a min.

Someone mentioned earlier....mainline guys look at you with surprise if asked about company pressure on fuel. Never have to arm wrestle with the dispatcher for more. Plus, 2 engine start at the gate is common practice. An Airbus or 737 burns 3x as much fuel AT IDLE than the 175 does in cruise.