The temperature coefficient significantly affects the energy output of solar panels by quantifying how their efficiency changes with temperature variations above the standard testing condition of 25°C (77°F). This coefficient is expressed as a percentage decrease in power output per degree Celsius increase in temperature.
How Temperature Coefficient Affects Solar Panel Output
- Negative correlation with temperature: Solar panels generally have a negative temperature coefficient, meaning their efficiency decreases as their temperature rises. For example, a temperature coefficient of -0.4% / °C indicates that for every 1°C increase above 25°C, the panel’s output drops by 0.4%.
- Efficiency loss accumulates with temperature rise: Solar panels operate best around 25°C but can reach surface temperatures of 50-65°C or even higher under direct sunlight. Given this, even a modest coefficient can lead to significant power losses. For instance, a panel with a -0.41% / °C coefficient operating at 65°C (40°C above 25°C) can lose around 16.4% of its rated power. This means a 260W panel might deliver only about 217W at that higher temperature.
- Voltage drop drives power losses: The efficiency loss mainly comes from a decrease in the solar cell voltage as temperature increases, which outweighs the slight increase in current output, resulting in a net drop in power.
Variations by Panel Type and Brand
- Temperature coefficients vary by solar panel technology and manufacturer. Monocrystalline and polycrystalline silicon panels typically have coefficients ranging from about -0.29% to -0.5% / °C, with some high-quality panels like those from REC Group and Panasonic achieving as low as -0.24% / °C.
- Thin-film solar panels tend to have lower temperature coefficients (around -0.2% / °C), making them less sensitive to temperature increases compared to crystalline silicon panels.
Practical Impact and Mitigation
- In moderate climates, temperature-induced efficiency losses are often small and may be negligible for many users. However, in hot climates or during heat waves, these losses can become significant.
- Installation methods like mounting panels a few inches above the roof to allow airflow and using thermally conductive substrates help reduce panel temperature and mitigate efficiency loss.
- Choice of roofing material also affects panel temperature. Light-colored or reflective roofs reduce panel temperature, while dark or heat-absorbing roofs increase it, thereby impacting the energy output.
Summary Table of Temperature Coefficients for Popular Panels
| Brand | Temperature Coefficient (% / °C) | Notes |
|---|---|---|
| REC Group | -0.24% | Among best for low temp impact |
| Panasonic | -0.24% to -0.29% | High efficiency and low losses |
| Maxeon | -0.27% to -0.38% | Premium panels with good ratings |
| SunPower | -0.29% to -0.38% | High efficiency, moderate losses |
| Q CELLS | -0.30% to -0.42% | Average range |
| Thin-film | ~-0.20% | Lower sensitivity to heat |
In essence, the temperature coefficient defines how much a solar panel’s power output will decrease as it heats up above 25°C. Since solar panels can get significantly hotter than ambient temperatures under strong sunlight, understanding and selecting panels with a low temperature coefficient improves energy yield, particularly in warmer climates. This consideration complements other factors like overall efficiency and installation environment in optimizing solar system performance.
References
This analysis is based on detailed explanations and data from multiple sources covering solar panel temperature effects and coefficients.
Original article by NenPower, If reposted, please credit the source: https://nenpower.com/blog/how-does-the-temperature-coefficient-affect-the-energy-output-of-solar-panels/
