We are offering stand-alone inverters, used in isolated systems where the inverter draws its dc energy from batteries charged by photovoltaic arrays andor other sources, such as wind turbines, hydro turbines, or engine generators. Many stand-alone inverters also incorporate integral battery chargers to replenish the battery from an ac source, when available. Normally these do not interface in any way with the utility grid, and as such, are not required to have anti-islanding protection.