You will get about 6V between the mains neutral and ground and you can use that voltage for free, it does not get metered. Although you will possibly get put in prison if the electricity company catch you doing it.
Come, come Mike you really shouldn't encourage this sort of behaviour.
If a neutral feeder fault (open circuit) occurs anywhere in the domestic distribution side between the substation and the home then the neutral line within the house could rise to line voltage.
I found a strange problem though.
What is ttyACM0 & ttyACM1 ?