Energy storage batteries provide an eco-friendly piece of mind from power outages. They also form a cornerstone of the larger societal shift to electrification, enabling owners to get the most benefit from solar panels. For example, excess electricity generated by solar panels during the day can be stored and used to charge an electric vehicle at night. Furthermore, fully off-grid and self-sustaining electricity is possible during power outages. Any number of Powerwalls can be strung together to make a larger battery back-up system as needed.