I want to put this GSM shield into my car to be able to access services from my smartphone, ie turn the heating on/off.
Is the power consumtption of the GSM shield and the arduino board negligible? I mean what if I don't need my car for 2 weeks, will the battery be empty?
As far as I'm concerned people recommend 12V 2amps to run the GSM module. However, from my own experience, 12V 1amp is enough.
If I try to run the module just though USB connection without an external source it doesn't connect, so I guess the power consumption is not that negligible.
All Arduinos use an linear regulator. Linear regulators have a low efficiency, if you can power it with switching regulator, you can lower power consumption alittle. If you replace the onboard regulator with a switching type you can llower the power consumption even more. But that is of course more difficult.