My thoughts as well when I read that.. Extra gas can be stored in cans. You might argue that you could have some backup batteries as well, but I'm guessing a single 12v automotive battery isn't going to come close to matching the energy in five gallons of gas. Edit: After running some rough calculations/estimates, it appears that you would need approximately four 12v batteries (rated for 65Ah) to match the energy potential of a five gallon gas can.