Photovoltaic system and is typically less useful than a calculation of return on investment. While it is typically calculated to be between 10 and 20 years, the financial payback period can be far shorter with incentives. Due to the low voltage of an individual solar cell (typically ca. 0.5V), several cells are wired "(also see copper used in PV systems)" in series in the manufacture of a "laminate". The laminate is assembled into a protective weatherproof enclosure, thus making a photovoltaic module or solar panel. Modules may then be strung together into a photovoltaic array. In 2012, solar panels available for consumers
Nominal power (photovoltaic) resistive load on the module between an open and closed circuit (between maximum and minimum resistance). The highest power thus measured is the 'nominal' power of the module in watts. This nominal power divided by the light power that falls on a given area of a photovoltaic device (area × 1000 W/m) defines its efficiency, the ratio of the device's electrical output to the incident energy. The nominal power is important for designing an installation in order to correctly dimension its cabling and converters. If the available area is limited the solar cell efficiency and with it the nominal power