Using a car battery for power lasted for months, when we rigged one up. So only charging the Car battery once or twice a year.
The item above states.
Power Supply Voltage: 12 vdc 1Amp max
1 x DC DC lead to connect to Battery or Portable Power Supply
Its one of the better solutions to a location without power.
There are others out there.
I think at one point we contemplated hooking it up to the nearest lamp post. But decided not too in favour of the car battery.