PV modules temperature coefficient.

Solar PV modules temperature coefficient is one of the most important specification after the power in Watt peak. You would like a PV module that generates as much kWh as possible per year.

The temperature coefficient determines, among other things, the power under "real" conditions (low light performance is different). This article explains what the influences, increase in temperature of the solar panel does have for PV energy production and power output.

PV modules temperature coefficient

What does the temperature coefficient mean?

PV panels efficiency and temperature coefficient is in every datasheet of a solar PV panel manufacturer brand. It indicates what the temperature effect is. The temperature coefficients indicate what happens to the power (W), the voltage (V) and the current (A) if the temperature rises by 1 degree.

The assets are most important to you. If the module gets a degree warmer, it will perform a certain percentage worse. Below you can see a table of solar panels and the corresponding temperature coefficients.

By far the best is the Panasonic HIT and the Solar Frontier panels. Panasonic is in the highest price segment, but surprisingly, Frontier is in the lowest priced class. It is due to the cheap production method of thin film panels and low power.

I think this is the reason why panel manufacturer Frontier performs well on an annual basis. Not because they do so well in cloud cover (we see the opposite).

Most panels have a temperature coefficient of around -0.4% / degrees celsius. Panasonic has very high efficiency and the best solar cell technology.

Temperature coefficient Pmpp (% / ° C) Power loss at 60 ° C panel
Panasonic HIT N325 Wp -0.29 -11.6
Solar Frontier 170Wp -0.31 -12.4
BenQ Sunforte 330Wp -0.33 -13.2
LG NEON2 315Wp -0.38 -15.2
Sunpower E20 330 Wp -0.38 -15.2
BISOL Premium black 280Wp -0.39 -15.6
Q Cells Q.Plus G3 275Wp -0.41 -16.4
LG MonoX 2 285Wp -0.42 -16.8

Completely black or a white back sheet?

The above story shows that a higher temperature is detrimental to the performance. An utterly black cell will warm up sooner than a PV module with a white back sheet. That is why all high-efficiency panels have a white back sheet.

This few degrees difference ensures a slightly higher yield on an annual basis. Suppose it is always 5 degrees colder, this saves around four percent in return. Because it is warm in Portugal most of the year, the yield is lower then the calculation shows.

Temperature coefficient of the voltage - inverter selection

The solar panel temperature coefficient of the voltage is important in the choice of the inverter. Not every installer takes this into account. It is nevertheless, important.

The temperature coefficient of the voltage determines the voltage of your PV module at a certain temperature. The colder, the higher the voltage. If it freezes -20 degrees, the voltage can be much higher than with the standard test conditions of 25 degrees.

This voltage can be so much higher that you inflate your inverter. That is because the input voltage is too high. To calculate how much higher the voltage is at a shallow temperature of -20 degrees.

Suppose the temperature coefficient of the voltage is -0.28% / ° C (LG NEON 2 315Wp). Then the voltage at -20 ° C: -0.28 * -45 = 12.6 percent higher. Sometimes enough to blow up the inverter. Many inverter manufacturers have a design tool that takes this into account.