Does temperature impact solar panel performance?

Published: 11 May 2019

What happens when the environment gets too hot, or cold? What impact does the temperature have on the performance of solar panels and how can we measure it?

With the ongoing incentives to acquire your own residential solar installation, a lot of questions and misunderstandings have arisen. One of the most common question being ‘how does temperature impact the performance solar panels?‘. Let’s try to get some insight into the impact of ambient temperature on the system’s efficiency.

Solar panels are designed to be installed outdoors, harvesting energy from the sun, but what happens when the environment gets too hot, or cold? 

Does it matter to the photovoltaic system (PV system)? The answer is yes. 

Commonly people think more sun equals more heat generating more electricity. However, this is not entirely true. 

Different solar panels have different reactions related to the ambient temperature, but in all cases, the heat increase reduces their efficiency. This can be translated as a decrease in power output as it lowers the panel’s voltage.

Home solar panels are usually designed for maximum efficiency at 25°C as the cell temperature (Standard Test Condition (STC) temperature). However, they could get as hot as 65°C.

Ways to measure the effect of temperature on solar panels

One way to consider the voltage and efficiency variations according to the temperature is with the use of correction factors. Watch this video to understand how it’s done: 

What effect does temperature have on solar panels?

Another common way is considering the temperature coefficient. 

This variable represents a percentage often found in the datasheet of the panel, associated with a specific electrical variable. 

The last one is normally given as a negative percentage that reveals the impact of the temperature in the solar panel, reducing that percentage value from the efficiency for every 1°C rise in the ambient temperature, or increasing that percentage value from the efficiency for every 1°C drop in the ambient temperature.

As an example, if a panel is designed to operate at 25°C with maximum efficiency and has a temperature coefficient of -0.50%, it means that if it reaches 45°C on a hot sunny day, it would result in a maximum power output reduction of 10%. 

This sounds like something you could live with, right?

But when you consider a whole year with this output reduction and the other usual factors that prevent the system from working at optimal performance, then it becomes a serious matter.

How to get the best out of your solar panels

  • In the panel making process, a thermally conductive substrate must be used to help vent the excess heat from the glass layer.
  • The installer must consider elevating the panels a few centimetres off the roof. Some kind of ventilation system may need to be added to the solar array to ensure that there will be a free air flow above and below the panels when they are mounted. For example, fans, or water evaporative cooling could be used.
  • When choosing the location of the PV System, consider installing the panels where there is good natural ventilation such as a crosswind.
  • Be cautious about hosing down your panels during the hottest part of the day, as the sudden temperature shock could make the glass crack and irreversibly damage your panels.
  • When your panels are covered by snow (rarely the case for Australia), do not try to get it off as you might damage the panel. Allow it to slide off on its own, or hire a professional team to do the job and clean the panels when needed.
  • Always keep in mind the temperature coefficient. Operating in temperatures colder than the designed ambient temperature will imply positive results, increasing the panel’s efficiency and power output. But warmer environments may require the need for modules with a temperature coefficient, to reduce the possible temperature impact.
  • The temperature coefficient is also extremely important when considering the output voltage limits, as it cannot surpass the maximum allowed voltage at the inverter’s input. Neither can go lower than the minimum voltage needed for the inverters and the energy storage system used. For example, if the output voltage of the module goes lower than the minimum needed by the battery pack installed, then it might not be able to be charged properly, wasting a substantial amount of solar energy.

Conclusion

Finally, we must know that cold, but sunny days are the optimal weather condition for the best solar panel performance. 

On the other hand, warm and sunny days might imply investing in better ventilation systems or lower temperature coefficient technologies. 

Depending on where you live, you must consider the weather cycles as well as the maximum and minimum temperatures that your location is known to achieve.

Besides that, we must consider the maximum and minimum limit voltages of the solar installation. 

Most of the time is simpler and better to go for the lowest temperature coefficient when selecting your solar panels.

Find out more about solar panels on our product page!

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