Tesla have come up with Powerwall, a home battery system that charges using electricity from solar panels, or when utility rates are low & can power your home in the evening. It provides independence from the grid & security for an emergency backup when the power goes out. It works somewhat like a generator, especially for areas that are prone to storms or unreliable electricity. It will also be designed for businesses to reduce peak electricity demands and to shift energy consumption if required. Click here to see more details on the Tesla Powerwall.