Photovoltaic (PV) devices convert light directly into electricity and should not be confused with other solar technologies such as concentrated solar power (CSP) or solar thermal for heating and cooling. The key components of a PV power system are various types of photovoltaic cells (often called solar cells) interconnected and encapsulated to form a photovoltaic module (the commercial product), the mounting structure for the module or array, the inverter (one or multiple, essential for grid-connected systems and required for most off-grid systems) the cabling to connect the modules with each other and with the inverter(s), the storage battery and charge controller (for off-grid systems but also increasingly for grid-connected ones).