Solar Power

Solar energy glossary of terms

Below are some terms and abbreviations to help you to navigate the solar energy specifics.

  • NMOT – Normal Module Operating Temperature (NMOT) this is a 20°c Ambient temp, 800 W/m2 Irradiance. This is more in line with real word conditions and my suggestion is to use this when sizing your solar park. For example a Leapton LP182*182-M-60-MH solar panel with STC rating 450 watts is 330 watts in NMOT rating.
  • NOCT – Nominal Operating Cell Temperature (NOCT)
  • Open circuit voltage – The open circuit voltage is the maximum voltage that the solar panel can produce with no load on it (i.e. measured with a multimeter across the open ends of the wires attached to the panel). If two or more panels are wired in series it will be Voc of panel 1 + Voc of panel 2, etc
  • STC – Standard Test Conditions (STC). These are industry standard conditions under which all solar PV panels are tested to determine their rated power and other characteristics. When a panel is advertised as having a capacity of 350Wp for example, this is the power it is expected to produce under STC.
    Cell temperature: 25°C
    Irradiance: 1000 W/m²
    Air mass: 1.5