Solar Panel Output Calculator

Calculate the real output of a panel after temperature, soiling and age derating.

About Solar Panel Output Calculator

Panels are rated at 25 °C but run far hotter in sunlight, so a 45 °C cell temperature alone costs about 7 per cent. Degradation adds roughly half a per cent per year permanently. Hot climates deliver less output per installed watt than temperate ones despite more sunshine, which is why temperature coefficient matters when selecting panels.

Formula

Solar Panel Output

Output = rated × (1 − temperature loss − degradation − soiling)

temperature coefficient: Percentage output lost per degree above 25 °C
degradation: Typically 0.5% per year of permanent capacity loss

Worked example

With the default values below, Solar Panel Output Calculator returns Actual Output of 376.250. Change any input above and every figure here is recalculated in your browser.

Inputs used

Panel rated powerminimum 1 W: 430 W
Cell temperatureaccepts -20–90 C: 45 C
Temperature coefficientaccepts -1–0 %/C: -0.35 %/C
Soiling lossaccepts 0–100 %: 3 %
Panel ageaccepts 0–40 years: 5 years

Results

Actual Output: 376.250 W
Loss From Temperature: 7.000%
Loss From Age: 2.500%
Total Loss Against Rating: 12.500%
Output per Square Metre: 188.13 W/m2

Step by step

1Values used
2Solar Panel Output
3Actual Output= 376.250 W
4Loss From Temperature= 7.000
5Loss From Age= 2.500
6Total Loss Against Rating= 12.500
7Output per Square Metre= 188.13 W/m2

Assumptions and limits

The result is derived only from the 5 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is Solar Panel Output calculated?

Output = rated × (1 − temperature loss − degradation − soiling) Panels are rated at 25 °C but run far hotter in sunlight, so a 45 °C cell temperature alone costs about 7 per cent. Degradation adds roughly half a per cent per year permanently.

Why does Solar Panel Output matter?

Hot climates deliver less output per installed watt than temperate ones despite more sunshine, which is why temperature coefficient matters when selecting panels.

What values do I need to enter?

This calculator takes 5 inputs: Panel rated power, Cell temperature, Temperature coefficient, Soiling loss, Panel age. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.