A grid-tied electrical system, also called tied to grid or grid tie system, is a semi-autonomous electrical generation or grid energy storage system which links to the mains to feed excess capacity back to the local mains electrical grid. … Conversely when excess electricity is available, it is sent to the mains grid.Definition: On-Grid Systems are solar pv systems that only generate power when the utility power grid is available. They must connect to the grid to function. They can send excess power generated back to the grid when you are overproducing so you credit it for later use.What is the difference between On-grid and off-grid solar power? On-grid means your solar system is tied to your local utility company’s system. … Being off-grid means you are not connected in any way to your grid’s power system or utility company. This is appealing because you are 100% self-sustaining your energy use.