Grid-connected or utility-interactive solar systems are designed to operate in parallel with and interconnected with the electric utility grid. The primary component in grid-connected PV systems is the inverter. The inverter converts the DC power produced by the solar array into AC power consistent with the voltage and power quality requirements of the utility grid, and automatically stops supplying power to the grid when the utility grid is not energized. A bi-directional interface is made between the solar system AC output circuits and the electric utility network. This allows the AC power produced by the solar system to either supply on-site electrical loads, or to back feed the grid when the solar system output is greater than the on-site load demand. At night and during other periods when the electrical loads are greater than the solar system output, the balance of power required by the loads is received from the electric utility. This safety feature is required in all grid-connected solar systems, and ensures that the solar system will not continue to operate and feed back onto the utility grid when the grid is down for service or repair.