Standard test conditions

Also known as STC

Standard test conditions are the laboratory conditions used to rate solar PV modules, usually shortened to STC on datasheets and module labels.

Standard test conditions are the reference laboratory conditions used to state solar PV module electrical ratings. For PV modules, STC normally means 1,000 W/m² irradiance, 25°C cell temperature and an AM1.5 light spectrum, so the label gives a comparable rating rather than a forecast of roof output. STC figures sit behind module power, kWp, voltage, current and efficiency values on datasheets, but actual generation also depends on orientation, inclination, shading, temperature, inverter limits, system losses and site conditions. STC is not the same as annual yield, an MCS performance estimate, NOCT or NMOT, export capacity, DNO acceptance, planning permission, warranty entitlement or installation quality.