Off-Grid Solar Calculators

Solar panels

Solar Panel Temperature Loss Calculator

STC ratings are at 25 °C cell temperature. A dark roof on a 35 °C afternoon can put cells near 60 °C. Crystalline modules typically lose about 0.35% of power per degree above 25 °C.

Inputs

Units
W
%/°C

Negative datasheet Pmax coefficient in %/°C. It is not converted when you switch to °F.

°F

Terms of Service

Results

Please tick the box above to display the Result.

Engineering methodology

P = P_STC × [1 + (γ / 100) × (T_cell − 25)], where γ is the datasheet Pmax coefficient in %/°C (typically about −0.25 to −0.45, often near −0.35). STC cell temperature is 25 °C, not air temperature. γ stays in %/°C even when the temperature field is shown in °F. Power-change percent = γ × (T_cell − 25 °C); do not multiply γ by a Fahrenheit increment. Cell temperature below 25 °C yields a power gain. Cell temperature can be estimated from NOCT as T_cell ≈ T_amb + (NOCT − 20) × G/800; this tool lets you enter T_cell directly and does not compute NOCT for you.

Frequently asked questions

How much power does a solar panel lose at 60 °C?

With γ = −0.35 %/°C, a 35 °C rise above 25 °C STC is 12.25% loss: a 400 W panel is about 351 W. Use the coefficient printed on your datasheet, not a generic −0.35, for a final design.

Is NOCT the same as cell temperature on a hot roof?

NOCT is a lab condition (typically 800 W/m², 20 °C ambient, 1 m/s wind). Real roofs can run hotter with low wind and high irradiance. Convert with T_cell ≈ T_amb + (NOCT − 20) × G/800, then enter that cell temperature here.

Does temperature also change Voc and Vmp?

Yes. Separate voltage coefficients apply. This calculator only scales Pmax. Charge-controller Voc limits still need the voltage coefficient and the coldest expected cell temperature.

More in this cluster

All tools in this cluster