Maybe its just part of some some collectively powered subsystem that remains powered for other fuel related functions like the evap control, fuel door, or some of those other whirry noises that happen. I wonder if you sit in the car all day, if the guage will register for a few minutes here and there as something else is occuring.

Two climate control systems, one inside and the other at the tailpipe.

2007 Camry Hybrid (in service June 2006)
FE: 6.77L/100km (34.8 mpg) over 37750km (23450mi)
75% city - Ave trip 20 min - 2 Winters