These stand alone solar inverters are called such because they do not need to be hooked up into a solar panel. Instead, it draws its direct current (DC) power from batteries which are charged by photovoltaic (PV) arrays or other resources such as engine generators, hydro turbines and wind turbines. There are a lot of these stand alone inverters which integrate vital battery chargers to refill the battery coming from an alternating current (AC) source whenever possible. Because these inverters are isolated from utility grids, they do not require anti-islanding protection.