This is not to live of the grid, but when there is no access to the grid and away from the vehicle like camping, at the beach or the park. At best with a fully set of charged batteries, an iBook can go an hour or two, four if one is using an CF or SSD. Advertised battery life was never what I met them to be. The MacBook Air has an advertised battery life of 6 hours, I never met one that did that. At most I have ever seen was 2.5 hours. But an iBook I fixed up and put a CF/SSD into does run for up to 3+ hours on a good battery. But after that, either I have to carry more batteries, use a "Battery extender" which is a flat battery pack that fits on the bottom of the laptop and connects to the power port, find a nearby outlet, carry a generator or a solar panel. The Solar Panel seems like the best option (besides freaking NYC/NYS is passing laws that limits the use of portable gas powered generators... Grrrr...).

This is just an idea I want to test, and have all winter to build.