Capacity is the amount of electricity a generator can produce when it's running at full blast. This maximum amount of power is typically measured in megawatts and helps utilities project just how big of an electricity load a generator can handle. Solar Photovoltaics (PV), also known as solar cells, are electronic devices that convert sunlight directly into electricity.An off-grid PV system refers to an installation that is not connected to the electricity grid. This means that all the energy produced is stored and used on site. Essentially, off-grid PV systems operate from the energy stored in a battery bank.