A grid-tied electrical system is a semi-autonomous electrical generation which links to the mains to feed excess capacity back to the local mains electrical grid. Grid systems do not store energy and therefore need no back up, thus no battery bank. With no storage losses, the system is are easy to monitor and measure performance. There is a benefit to you as the homeowner in the form of compensation for the energy that you put back into the grid. Through net-metering it credits at a certain rate, applied to your monthly bill for every KWh you put back into the grid.