On-the-grid systems uses the grid as a storage using net metering credits. If your solar energy system produces more than your facility's need the energy excess feeds back to the grid and gain you net metering credits. You use your credits when your energy need is higher than your system production.
How solar energy works? PV cells converts sunlight to DC current. Inverters then convert the DC current into AC. The energy gets used by your business or house and the energy excess gets pushed back into the grid for credit. You use the credit when your system is producing less energy than you need.