When choosing solar panels for a hot city like Chennai, most people focus on wattage and efficiency. But there’s another factor that has a direct impact on your daily power generation—the temperature coefficient.
What Is Temperature Coefficient?
The temperature coefficient tells you how much a solar panel’s efficiency drops as temperature increases.
Solar panels are tested under standard conditions (25°C). But in real life—especially in Chennai—panel temperatures can easily reach 60–70°C on rooftops.
The coefficient is usually expressed as a percentage per degree Celsius.
For example:
- A panel with -0.35%/°C means:
- For every 1°C rise above 25°C, output drops by 0.35%
Ongrid solar system Chennai home
Simple Formula
P=Prated×(1+γ(T−25))P = P_{rated} \times \left(1 + \gamma (T – 25)\right)
Where:
- PP = Actual power output
- PratedP_{rated} = Rated power at standard conditions
- γ\gamma = Temperature coefficient (negative value)
- TT = Panel temperature in °C
Why Solar Panels Lose Efficiency in Heat
Solar panels generate electricity using sunlight, but excess heat actually reduces voltage, which lowers power output.
So:
- More sunlight = good
- More heat = bad
That’s why temperature coefficient is critical in hot regions.
Chennai Reality: Why This Matters More Here
Chennai has:
- High ambient temperatures (30–40°C)
- Strong sunlight
- Concrete rooftops that trap heat
This causes panel surface temperatures to rise much higher than air temperature.
Typical rooftop conditions:
- Air temperature: 35°C
- Panel temperature: 60–70°C
That’s 35–45°C above test conditions, leading to significant energy loss.
Real Example (Chennai Summer)
Let’s compare two panels:
Panel A:
- Temperature coefficient: -0.40%/°C
Panel B:
- Temperature coefficient: -0.30%/°C
If panel temperature reaches 65°C:
- Temperature rise = 65 – 25 = 40°C
Power loss:
- Panel A: 40 × 0.40% = 16% loss
- Panel B: 40 × 0.30% = 12% loss
👉 That’s a 4% difference in output, every hot day.
Over a year, this becomes a big difference in electricity generation and savings.
Good vs Bad Temperature Coefficient
- Better (lower loss): around -0.30%/°C
- Average: around -0.35%/°C
- Poor: -0.40%/°C or worse
👉 The closer the value is to zero, the better the performance in heat.
Which Panels Perform Better in Heat?
TOPCon Panels
- Typically have better temperature coefficients
- Perform more efficiently in high heat
- Ideal for Chennai conditions
Mono PERC Panels
- Slightly higher losses in heat
- Still reliable but less efficient in extreme temperatures
Bifacial Panels
- Can help slightly due to better airflow (if elevated)
- But temperature coefficient still matters
How to Reduce Heat Loss on Your Rooftop
Even with a good panel, installation plays a big role.
1. Elevate Panels
- Leave space between roof and panel
- Improves airflow and cooling
2. Use Proper Mounting Structure
- Avoid flush mounting directly on hot concrete
3. Choose Light-Colored Roof Coating
- Reflects heat and reduces panel temperature
4. Select High-Quality Panels
- Lower temperature coefficient = better long-term output
Why This Affects Your Savings
Higher heat loss means:
- Less daily energy generation
- Lower savings on electricity bills
- Longer payback period
In Chennai, where heat is constant, even a small efficiency difference can result in thousands of units lost over 25 years.
Final Verdict
- Temperature coefficient is one of the most important factors for Chennai solar systems
- Panels with lower (better) coefficients perform significantly better in summer
- Ignoring this can reduce your system’s real-world performance
👉 For Chennai homes in 2026:
Choose panels with -0.30%/°C or better, preferably TOPCon technology, for maximum efficiency and savings.
FAQs
1. What is a good temperature coefficient for solar panels?
Anything around -0.30%/°C or lower is considered good.
2. Does higher temperature always reduce solar output?
Yes. Heat reduces voltage, which lowers overall power generation.
3. Is temperature coefficient more important than efficiency?
In hot cities like Chennai, both are equally important.
4. Do all panels heat up the same way?
No. Design, materials, and installation affect heat buildup.
5. Can installation reduce temperature losses?
Yes. Proper elevation and airflow can significantly improve performance.