Nominal power (photovoltaic) be described as having "one kilowatt-peak" in the meaning "one kilowatt of peak power". Similarly outside the SI, the peak power is sometimes written as "P = 1 kW" as opposed to "P = 1 kW". In the context of domestic PV installations, the kilowatt (kW) is the most common unit for peak power, sometimes stated as kW. The output of photovoltaic systems varies with the intensity of sunshine and other conditions. The more sun, the more power the PV module will generate. Losses, compared to performance in optimal conditions, will occur due to non-ideal alignment of the module in
Photovoltaic effect electric energy. The photovoltaic effect can also occur when two photons are absorbed simultaneously in a process called two-photon photovoltaic effect... The photovoltaic effect was first observed by French physicist A. E. Becquerel in 1839. He explained his discovery in "Comptes rendus de l'Académie des sciences", "the production of an electric current when two plates of platinum or gold immersed in an acid, neutral, or alkaline solution are exposed in an uneven way to solar radiation." Besides the direct excitation of free electrons, a photovoltaic effect can also arise simply due to the heating caused by absorption of the light.