Solar Panel Temperature Calculator (NOCT and Power Loss)

What this tool does

Solar cells run well above the air temperature, and silicon loses output as they heat up — often around 0.3 to 0.4 % of power for each degree above 25 °C. The datasheet's NOCT is the cell temperature in 800 W/m² sunlight, 20 °C air and a 1 m/s breeze; the cell temperature then rises in proportion to the irradiance. A hot afternoon with cells at 60 °C costs a panel roughly 12 % of its rated power before any other loss, which is why mounting that lets air circulate behind the panels pays off. This is a simple estimate that ignores wind and mounting.

Formula

T_cell = T_amb + (NOCT − 20) ÷ 800 × G · P = P_STC × (1 + γ × (T_cell − 25)) × G ÷ 1000

Variables

Symbol	Meaning	Unit
`ta`	Ambient temperature	°C
`noct`	NOCT of the panel	°C
`g1`	Irradiance on the panel	W/m²
`pm`	Rated power of the panel (STC)	W
`gm`	Power temperature coefficient	%/°C
`TC`	Cell temperature	°C
`PO`	Power the panel delivers	W
`EF`	Effect of the cell temperature on power	%

Worked example

Ambient temperature30 °C
NOCT of the panel45 °C
Irradiance on the panel800 W/m²
Rated power of the panel (STC)400 W
Power temperature coefficient-0.35 %/°C

Cell temperature55.0 °C
Power the panel delivers286 W
Effect of the cell temperature on power-10.5 %

Limitations

The result is an estimate based only on the values you type. Real situations often include factors this calculator does not know about.
Coverage and consumption figures vary between products. Take the values from the manufacturer's datasheet for the product you are actually using.