For many reasons, some people don’t want to depend entirely on their utility company to provide them with power. If there is a power outage or blackout, your system will go down, too, because it is grid-dependent or grid-tied. However, if you purchase an energy storage system with your solar array, your system will not go down even if the grid is down. This type of system is referred to as a solar-plus-storage system. There really is no downside to it.