Does hot weather affect the efficiency of my solar energy system?

Does hot weather affect the efficiency of my solar energy system? Absolutely! During summer conditions, temperatures rise and solar panels heat up. The result: efficiency loss.

Efficiency loss

In the graph below, we can see that as the panel temperature increases, the MPP voltage drops. The power of a panel is: MPP voltage x MPP current (P = Umpp x Impp). When the current remains the same and the voltage decreases, the output power is lower. So, at higher temperatures, less power is delivered from the inverter.

Real-world example: solar panel performance

Above is a performance graph of a solar energy installation on a sunny day with high temperatures of around 30 degrees Celsius. The maximum output values are around 570 Watts, despite full sunlight. Due to the high panel temperature, the power drops.

Now take a look at a day with a significantly lower outdoor temperature. Here we see peak performance values that even exceed the STC rating of 3 x 240Wp. This is partly thanks to the panel’s positive tolerance, which helps deliver more power. However, as you can see, this peak is brief. The panel heats up and the power output decreases again.

Conclusion

In hot weather, the actual power (Watt values) is lower, but due to consistent sunshine, total yield remains high compared to cloudier days. With inverters designed based on minimum string length, the MPP voltage may drop below the required minimum on very hot days, causing the inverter to stop producing power. Fortunately, inverters are built to handle this, so no damage occurs.