The inverter is perhaps the most important part of any solar system connected to the grid; it can be considered the brain of the system. The inverter determines the voltage at which the system switches on and off. It determines when the solar panels receive enough light in the morning to start sending energy to the grid and it also determines when it is dark and turns off the system until the next day. The inverter contains all the safety algorithms, the most common is to maintain the system shut-off for at least 5 minutes after a loss of voltage in the grid. This protects workers making repairs in the utility network. Grid-tie inverters must include a Ground Fault Detection and Interruption (GFDI) device which detects any electric current in the ground circuit. The most recent inverters include an Arc Fault Detection and Interruption (AFDI) device which detects any arc in the circuit. Most grid-tie inverters will include a main interrupter that will completely disconnect the system. In this section we have three types of grid-tie inverters. Central or String Inverters are the most common, especially in residential solar electric systems. In cases where individual monitoring is required or shading and obstacles are present, using Microinverters is recommended. Central inverters with Battery Backup allow you to have a solar system connected to the grid and backup batteries to provide power when the grid fails.