Nominal operating cell temperature

NOCT (Nominal Operating Cell Temperature), or the closely related NMOT (Nominal Module Operating Temperature) label on some module datasheets, is a solar PV module temperature value measured under defined outdoor-style test conditions. The common NOCT conditions are 800 W/m² irradiance on the module, 20°C ambient air, 1 m/s wind and an open-back or free-air mounting context, rather than the 25°C cell temperature used for STC (standard test conditions). The value helps performance models and temperature-coefficient calculations estimate how hot cells may run in use, but it is not a roof-temperature guarantee, annual yield forecast, MCS performance estimate, DNO acceptance, warranty verdict or proof of installation quality.