Solar panels need to store the energy they create somewhere. Storage takes place in solar batteries or a portable power station. A single battery should suffice if you want a backup for personal devices and essential appliances when the grid goes down. However, if you want to go off-grid entirely, you could need as many as twelve solar batteries (or more, depending on capacity) to ensure you have enough power to keep you going. The right number ultimately depends on your energy consumption needs and the capacity of the batteries.