Understanding Solar PV Power and Energy Yield
A first-order estimate of photovoltaic system output starts from the module nameplate rating under Standard Test Conditions (STC: 1000 W/m², 25 °C cell temperature). Real-world irradiance and temperature then scale the DC power, after which the inverter efficiency converts it to usable AC power.
Temperature Derating
Most crystalline silicon modules lose roughly 0.3–0.45 % of power for every degree Celsius above 25 °C. The temperature coefficient γ is therefore applied as a linear correction: P = P_STC × (1 + γ · (T_cell – 25)). Hot climates can easily reduce output by 10–20 %.
Daily Energy and Performance Ratio
Multiplying AC power by the location’s peak sun hours (equivalent hours at 1000 W/m²) gives a practical daily energy figure. The performance ratio compares actual AC output against the irradiance-scaled nameplate capacity and is a useful health metric for operating plants.