ALONE, good question. I definitely have to have it so it is something I will have to ask the company. I do know that this particular company screens it's drivers for sleep apnea and if they are diagnosed, then they have to get one. But it sure wouldn't be good if I got out on the road and I couldn't plug it in.
Almost every sleeper or there either has the standard power outlets or a few of the 12v cigarette lighter outlets, and you can get a single insurer that plus into the 12v for only $50.