Solar Panel Temperature Coefficient Explained — Why It Matters
What Is Temperature Coefficient?
The temperature coefficient of Pmax tells you how much power a solar panel loses for every degree Celsius above the 25°C standard test temperature. It is expressed as a negative percentage per degree (%/°C). A lower (less negative) value means better performance in heat.
Why It Matters in Hot Climates
In the UAE, panel surface temperatures regularly reach 65–75°C in summer — that is 40–50°C above STC. The difference between a −0.40%/°C panel and a −0.29%/°C panel at 70°C is significant:
| Panel | Temp Coeff. | Loss at 70°C | Output Retained |
|---|---|---|---|
| Polycrystalline | −0.40%/°C | 18.0% | 82.0% |
| Mono PERC (Hi-MO 6) | −0.34%/°C | 15.3% | 84.7% |
| N-type TOPCon (Hi-MO 7) | −0.29%/°C | 13.1% | 86.9% |
| HJT | −0.25%/°C | 11.3% | 88.7% |
How to Use Temperature Coefficient in Design
Multiply the coefficient by the temperature difference above 25°C:
Power loss (%) = Temp coefficient × (Cell temp − 25°C)
For Hi-MO 7 at 70°C: −0.29% × 45 = −13.1% loss
LONGi's Temperature Advantage
The Hi-MO 7's −0.29%/°C coefficient is among the best for TOPCon technology. In a UAE summer, this translates to approximately 2–4% more annual energy compared to Mono PERC panels, compounding over the 30-year warranty period.
Frequently Asked Questions
What is a good temperature coefficient?
Below −0.30%/°C is excellent for hot climates. LONGi Hi-MO 7 achieves −0.29%/°C. HJT panels can reach −0.24%/°C but at significantly higher cost.
Does temperature coefficient change over time?
No. The temperature coefficient is a fixed physical property of the cell technology and does not change with age or degradation.
Can I improve temperature coefficient after installation?
No, but you can reduce cell temperature through proper ventilation (100mm+ clearance) and appropriate tilt angle, which indirectly improves output.
Frequently Asked Questions
What is a good temperature coefficient?
Below −0.30%/°C is excellent. LONGi Hi-MO 7 achieves −0.29%/°C.
Does it change over time?
No. It is a fixed physical property of the cell technology.
Can I improve it after installation?
No, but proper ventilation reduces cell temperature, indirectly improving output.
