The temperature coefficient is a key spec sheet number that determines how much a solar panel’s output drops as it heats up beyond its rated test temperature. Lower (more negative) temperature coefficients mean better hot-weather performance — HJT panels lead with -0.24%/°C, PERC lags with -0.45%/°C.
Temperature Coefficient by Cell Technology
| Cell Technology | Typical Temperature Coefficient |
|---|---|
| HJT | -0.24% to -0.26%/°C |
| IBC | -0.29% to -0.35%/°C |
| TOPCon | -0.29% to -0.34%/°C |
| PERC | -0.35% to -0.45%/°C |
Understanding the Math
The temperature coefficient represents percentage output loss per degree Celsius above the 25°C rating point — a panel with -0.35%/°C loses 0.35% of output for every degree above 25°C the cell reaches.
Why This Matters for Hot Climates
Panels can reach 60-70°C+ in direct summer sun — at these temperatures, the difference between a -0.24%/°C and -0.45%/°C panel translates to a meaningful real-world output gap.
HJT vs. PERC vs. TOPCon
HJT panels offer the best temperature coefficient thanks to their heterojunction cell structure, followed closely by IBC and TOPCon — older PERC technology lags meaningfully behind in hot-weather performance.
When Temperature Coefficient Matters Most
Homeowners in consistently hot climates (Arizona, Texas, Southern California) benefit most from prioritizing panels with better temperature coefficients, since the real-world impact compounds over many hot days each year.
Get panel recommendations for your climate: (855) 427-0058
Frequently Asked Questions
What is the temperature coefficient?
The percentage output loss per degree Celsius above the 25°C rating point.
Which panel technology has the best temperature coefficient?
HJT, typically -0.24% to -0.26%/°C, the lowest (best) among common technologies.
Does temperature coefficient matter in cold climates?
Less so — it’s most impactful in consistently hot climates.
How hot do solar panels actually get?
60-70°C+ in direct summer sun, well above the 25°C rating point.
Should I prioritize temperature coefficient when buying panels?
Yes, especially in hot climates like Arizona or Texas.
Is PERC still a reasonable panel choice?
Yes for moderate climates, though TOPCon/HJT offer better hot-weather performance.
How much difference does temperature coefficient make in real terms?
Meaningful over many hot days per year, though it’s one of several factors in overall performance.
Summing Up
Temperature coefficient matters most for homeowners in hot climates choosing between panel technologies. For climate-specific panel recommendations, call (855) 427-0058 or visit us.solarpanelsnetwork.com.
Updated