The GPS uses a few mA, not significant unless you are leaving the car for weeks, the camera will use an unmeasurable amount in standby.
In parking mode it is recording the video to memory, either for the buffered video, or just for motion detection from looking for movement in the image, so the only saving over normal is only that it doesn't write to the memory card.
If the low voltage cutoff operates then that is also an unmeasurable amount.