I went out to start my truck and wait on my wife to come out and move her car. It was 19 degress, truck was plugged in all night. I fire it up and it goes to high idle. I'm noticing the grid heaters cycling when I notice my fuel pressure guage lose pressure everytime the grids cycle. It fluctuated almost a whole psi and then went back to normal when the grids shut off. It just goes to show how much juice they use. This was before the alternator cycled and got up to normal voltage.