solar cells are semiconductor devices that convert light to electricity. they have many applications. they have long been used in situations where electrical power from the grid is unavailable, such as in remote area power systems, earth-orbiting satellites and space probes, consumer systems, e.g. handheld calculators or wrist watches, remote radiotelephones and water pumping applications. more recently, they are starting to be used in assemblies of solar modules connected to the electricity grid through an inverter, often in combination with net metering.