For one, it's a battery hog (that, or the battery's too small), lasting about three hours in my tests before going back to the cradle or having to run plugged in (the power cable's reasonably long at eight feet).
To make the light travel enormous distances, thousands of volts of electricity are sent through the cable's copper sleeve to power repeaters, each the size and roughly the shape of a bluefin tuna.
As well as the island's power station, Guernsey imports electricity from the French grid via cable links between France and Jersey and between the islands.