PV Max Ambient Temperature for a Target Power

The highest ambient temperature a module still makes a target power.

Run the calculator

Example

You enter

Target power (W) 358
Module STC power (W) 400
Plane-of-array irradiance (W/m²) 800
NOCT (C, datasheet, default 45) 45
Power temp coefficient (%/C, e.g. -0.35) -0.35

You get

Max ambient temperature 30
Cell temperature at that point 55 C

Details, formula, and sources

Since a negative power coefficient means a hotter cell makes less. T_cell = 25 + (P/P_stc - 1) x 100/gamma, then T_amb = T_cell - (NOCT-20) x G/800. A 400 W module holding 358 W at 800 W/m^2 tops out at 30 C air (55 C cell). Answers 'how hot before it drops below target' instead of the power from a set air temp. Temperature derate only; the datasheet governs.

T_cell = 25 + (target_power/P_stc - 1) x 100/gamma; max_ambient = T_cell - (NOCT - 20) x G/800. The inverse of P = P_stc x (1 + gamma/100 x (T_cell - 25)) and T_cell = T_amb + (NOCT - 20) x G/800.

The PV NOCT cell-temperature model and the datasheet power temperature coefficient, by name, solved for the ambient temperature.

The NOCT model and temperature-coefficient derate are standard PV design relations (NREL / module datasheets). The module datasheet governs the coefficients.

Estimate. AHJ and licensed professional govern.

Field names used by the API: target_power_W, P_stc_W, G_wm2, NOCT_C, gamma, max_ambient_C, max_cell_C

NOCT model max ambient = T_cell - (NOCT - 20) x G/800PV design practice / NREL
Power derate inverse T_cell = 25 + (target/P_stc - 1) x 100/gamma; gamma ~ -0.35%/C siliconmodule datasheet
Temperature only no irradiance scaling and no soiling/wiring/inverter/shading lossesscope of this tile