Temperature Coefficient

What Is the Temperature Coefficient?

The temperature coefficient (TK Pmax) indicates by what percentage the power of a solar module decreases when the cell temperature rises one degree Celsius above the reference temperature (25 °C at STC). A typical value is -0.3 to -0.4%/°C.

Real-World Impact

On a hot summer day, cell temperature can easily reach 60—70 °C. With a temperature coefficient of -0.35%/°C, this means:

Cell Temperature	Power Loss	Remaining Power
25 °C (STC)	0%	100%
45 °C	-7%	93%
60 °C	-12.3%	87.7%
70 °C	-15.8%	84.2%

Differences by Technology

Cell Technology	Temperature Coefficient
Monocrystalline (PERC)	-0.34 to -0.38%/°C
TOPCon	-0.29 to -0.32%/°C
HJT	-0.24 to -0.26%/°C
Thin-film (CdTe)	-0.25 to -0.30%/°C

HJT modules have the best temperature coefficient and deliver relatively more power in heat.

Practical Tip

In hot regions or with flat-roof mounting with limited rear ventilation, a module with a low temperature coefficient is worthwhile. Adequate rear ventilation (at least 10 cm) can reduce cell temperature by 10—15 °C.