Solar batteries are charged when your PV (photovoltaic) panels are producing more energy than a building is using up. This means that you will now have access to an energy source that does not rely on the powerplants in your area. Thus, if a power outage would to occur in your area, solar batteries will continue to provide your building energy to keep running. Thus, solar batteries are a great idea if you want to live off the grid! With just a one-time cost for the battery, you can free yourself from high energy costs.