Solar Panel Temperature & Power Calculator
Enter one panel rating, sunlight on the panel plane, air temperature, wind, mounting style, and the panel temperature coefficient. The calculator estimates cell temperature, DC watts now, and the air temperature needed to reach a selected output.
Estimated power per panel344.86
- Estimated module temperature
- 64.38
- Estimated array DC power
- 3,448.62
- Temperature power change
- -13.78%
- Total change from STC power
- -13.78%
- Ambient temperature for target output
- 52.76
Temperature model details
| Value | Result |
|---|---|
| Back-surface temperature (°C) | 61.38 |
| Temperature factor | 0.86 |
| Target cell temperature (°C) | 82.14 |
Uses the Sandia coefficient set for open rack, glass/polymer modules.
This is an instantaneous DC estimate before inverter, wiring, soiling, shading, mismatch, and clipping losses.
How to use this calculator
- Enter the STC rated power for one panel and the number of panels in the array.
- Enter plane-of-array irradiance, ambient air temperature, and wind speed at about 10 meters above ground.
- Choose the closest Sandia mounting preset and enter the datasheet Pmax temperature coefficient.
- Set the target output percent if you want the reverse-solved ambient temperature.
How the temperature and power are calculated
Solar panels are usually rated at standard test conditions: 1000 W/m² of irradiance and a 25°C cell temperature. In the field, the cell temperature is often much higher than the surrounding air because the module absorbs sunlight and only part of that energy leaves as electricity.
This calculator uses the Sandia module-temperature form. The selected mounting preset supplies three published coefficients: a, b, and ΔT. First it estimates the module back-surface temperature:
Tm = Ta + E x exp(a + b x v)
Then it estimates cell temperature:
Tc = Tm + (E / 1000) x ΔT
- Ta is ambient air temperature in °C.
- E is plane-of-array irradiance in W/m².
- v is wind speed in m/s.
- Tc is the estimated cell temperature used for power correction.
The power correction uses the panel's Pmax temperature coefficient, entered as percent per °C and converted to a decimal:
Ft = 1 + g x (Tc - 25)
Ppanel = Pr x (E / 1000) x max(0, Ft)
Parray = N x Ppanel
The temperature power change is 100 x (Ft - 1). The total change from STC is 100 x (Ppanel / Pr - 1), so it includes both irradiance and temperature.
What moves the result most
Irradiance sets the main power scale. A panel at 800 W/m² starts at about 80% of STC output before temperature is considered. Cell temperature then trims or adds power through the datasheet coefficient. A module with a -0.35%/°C coefficient loses about 7% from temperature alone at a 45°C cell temperature.
Mounting and wind change how hot the module gets. Open-rack modules usually run cooler because air can move behind them. Close roof mounts and insulated backs retain more heat, which lowers DC power on hot sunny days. Strong wind reduces the Sandia heat term and can noticeably improve output.
Reverse target temperature
For the target output, the calculator solves the same equations backward. It first finds the cell temperature that would produce the selected percent of STC watts at the entered irradiance:
Tc,target = 25 + (((q / 100) / (E / 1000)) - 1) / g
Then it subtracts the Sandia heating terms to get the ambient air temperature:
Ta,target = Tc,target - E x exp(a + b x v) - (E / 1000) x ΔT
At zero irradiance, there is no power to scale, so the reverse result is unavailable. A zero temperature coefficient also makes the reverse equation undefined.
What this calculator leaves out
This is a steady-state DC power estimate, not an annual production model. It does not model clouds, angle-of-incidence effects, spectrum, shading, soiling, module mismatch, wire loss, inverter efficiency, inverter clipping, bifacial gain, or control behavior. The linear temperature coefficient is a datasheet approximation and becomes less dependable at extreme temperatures.
Worked example
Suppose one panel is rated at 400 W, the array has 10 panels, irradiance is 1000 W/m², air temperature is 35°C, wind speed is 1 m/s, and the mounting choice is open rack, glass/polymer. The Sandia coefficients are a = -3.56, b = -0.075, and ΔT = 3°C.
The back-surface temperature is 35 + 1000 x exp(-3.56 - 0.075 x 1) = 61.38°C. The cell temperature is 61.38 + 3 = 64.38°C. With a -0.35%/°C Pmax coefficient, the temperature factor is 1 - 0.0035 x (64.38 - 25) = 0.8622.
The estimated panel power is 400 x 1.0 x 0.8622 = 344.86 W, and 10 panels produce about 3448.62 W DC before other losses. The temperature-only power change is -13.78%, and the total change from STC is also -13.78% because irradiance is exactly 1000 W/m². A target of 80% of STC reverse-solves to an ambient temperature of about 52.76°C.
Common questions
Why is solar panel cell temperature higher than air temperature?
A solar module absorbs strong sunlight, converts only part of it to electricity, and releases the rest as heat. The cells sit behind glass and encapsulant, so their temperature can be much higher than nearby air, especially with weak wind or little rear ventilation.
Where is the Pmax temperature coefficient on a panel datasheet?
Look in the electrical characteristics or temperature ratings section for a line named Pmax, power, maximum power, or temperature coefficient of Pmpp. It is usually a negative percent per degree Celsius, such as -0.29%/°C or -0.35%/°C.
What is the difference between STC, NOCT, and NMOT?
STC is the laboratory rating condition: 1000 W/m² irradiance and 25°C cell temperature. NOCT and NMOT are operating-temperature tests that use lower irradiance and specified mounting and wind assumptions. This calculator does not use a single NOCT value; it estimates temperature from irradiance, air temperature, wind, and mounting coefficients.
How does rooftop mounting change panel temperature?
A roof-mounted panel with a small air gap usually runs hotter than an open-rack panel because less air passes behind it. Higher cell temperature reduces power when the Pmax coefficient is negative, which is the normal case for crystalline silicon modules.
Can a panel exceed its rated power in cold weather?
Yes, briefly. If irradiance is near or above 1000 W/m² and cells are colder than 25°C, the temperature factor can be above 1. Clean modules, bright sun, and cold wind can produce DC power above the STC nameplate before inverter limits or other losses are applied.
Is this an instantaneous estimate or an annual energy estimate?
It is an instantaneous DC power estimate for the conditions you enter. Annual energy modeling needs weather files, sun position, system orientation, shading, soiling, inverter behavior, and many hourly calculations.