Now I know this will come off sounding snarky but I really do think its a relevant issue. You want to be energy independent for green reasons yet are willing to spend a lot of money on special devices to do it. There are resources mined, refined, processed and manufactured in order to make each of these gadgets. In essence, your carbon footprint grows larger in your technological solutoons to reduce your carbon footprint. Id equate it to a single person buying an electric car to be "environmental" to offset the impact of the other car. The greenest way to reduce impact is to use equipment already manufactured / reuse/recycle. ride vintage bikes, use vintage equipment as much as posible, use paper road maps, the same rechargeable batteries, perhaps one smart phone (older model that would have hit the landfill?) Or none at all. Bottle generators work, not great but it prevents more waste. That seems more green and "off the grid" to me.