A gas or diesel generator is far more effective for the occasional power outage. It might not be as green but it’s hell of a lot cheaper and better suited for occasional infrequent use. Generally complete off grid power use deep cycle lead acid batteries because there are just better suited for the work load requirements. Lithium ion’s biggest strength is weight to power density which matters in cell phones, cars and planes but not so much in a house. That doesn’t stop Tesla from marketing Powerwall but it really doesn’t make much sense to do that over deep cycle marine battery storage.