An on-grid or grid-tied solar system is a system that works along with the grid. This means that any excess or deficiency of power can be fed to the grid through net metering (If presented) or it can be operated by Zero-Export Meter. Many residential users are opting for an On-grid solar system as they get a chance to enjoy credit for the excess power their system produces and save on their electricity bills. You will always have power either from the solar system or from the grid. They do not have batteries for any backup purpose.