How can STC watts be calculated for a photovoltaic (PV) system?

To calculate the STC (Standard Test Conditions) watts for a photovoltaic (PV) system, one must use the product of the voltage at maximum power (Vmp) and the current at maximum power (Imp).

Vmp represents the voltage at which the solar panel produces its maximum power output, while Imp is the current at that same maximum power point. When these two values are multiplied, the result is the maximum power output of the solar panel, typically expressed in watts. This is critical for system designers and installers as it helps in evaluating the expected performance of the PV system under standard test conditions (1000 W/m² of solar irradiance, 25°C cell temperature, and air mass of 1.5).

Using Voc (open-circuit voltage) or Isc (short-circuit current) instead of Vmp and Imp will not provide an accurate representation of the PV system's true power output since those values do not denote the operating conditions of the panel when it is actually generating electricity under load.