Do my solar power modules need to be cleaned?

By Jared T. Koch

The answer to the question above is yes, solar power modules do need to be cleaned. This is a critical aspect of maintenance that has only recently gained recognition in the solar industry.

Historically, many in the industry dismissed cleaning as an illegitimate need—but as the solar industry has evolved and our understanding of operations and maintenance (O&M) has deepened, the importance of regular cleaning has become increasingly clear.

However, there are still a lot of questions and misconceptions floating around today surrounding the frequency of cleaning, the purpose and importance of cleaning, what effect rain has on cleaning panels, and what types of soiling are harmful for panels.

Probably the most common question surrounding the cleaning of solar panels is, ‘How often do they need to be cleaned?’ There are several factors that all play a part in answering that question. In every case, these factors will include system size, geographic location, age of the system, and specific regional soiling challenges.

Using a Power Loss Study is one of the simplest, yet most precise ways to determine when cleaning is necessary. A system owner can conduct a Power Loss Study by simply cleaning a few modules and comparing the power output of the clean modules to the output of the same number of dirty modules. This quick and easy test will determine the power loss that is due to soiling. With this information, a conclusion can be drawn as to when the next cleaning is necessary.

One other simple test that can be done to check if a cleaning may be needed is to look back at the system’s output over its lifespan. Output will vary from month to month, so system owners need to keep the bigger picture in mind when looking at efficiency decrease. If the efficiency of the system has dropped significantly, soiling is often to blame and it may be time for a cleaning.

A common misconception within the industry is that cleaning is merely for aesthetics—this is far from the truth. While a clean, shiny module certainly looks impressive, the benefits extend well beyond appearance. Clean modules operate at peak efficiency. Dirt traps heat, causing the module to operate at a warmer than desired temperature, which can significantly decrease the lifespan of the modules if not addressed. Specifically, bird droppings create dangerous hot spots that can lead to cell damage if left untreated. Moreover, clean modules expel snow much more effectively than their dirty counterparts. Perhaps most importantly, cleaning your modules can result in substantial increases in energy production, which results in larger financial paybacks. 

Many ask about the extent of this improvement and, while there is variability, it is not uncommon to see boosts of between three percent to an outstanding 45 percent. Prioritizing the cleaning of your solar modules is not just beneficial—it’s essential for optimal performance and longevity.  

Many critics of solar cleaning claim that rain washes the modules, therefore cleaning is unnecessary. However, the rain is not enough; it will only rinse off a thin layer of dirt. To truly clean, you need some method of agitation. This can be provided by a professional solar washing company that uses proper methods for solar cleaning. These methods can include robotics or the use of manual brushing. In some extreme cases, specialized cleaners may even be required. For this reason, rain alone cannot clean the panels. 

Soiling can look very different depending on where the system is located geographically. Pollen is a very sticky type of soiling that will cling to the module glass. Once a layer of pollen has adhered to the module, more dust will settle on the surface and attach to the pollen. Loose dirt is another common soiling factor. Dirt becomes an issue when it is made wet by dew, only to be baked on by the sun the following day. After many cycles of this, the layer of soiling will continue to grow, reducing efficiency and the lifespan of the module. Cleaning is and will always be needed in these scenarios.

When cleaning is needed, always contact a professional, experienced cleaner who will safely and efficiently clean the system. And remember, the cheapest price quoted is not always the best value. 

In conclusion, cleaning is and will always be required at some time in a system’s life. Have you done a power loss study to determine if your system is operating efficiently?

Jared T. Koch is the founder of JTK, LLC and JTK Solar Solutions (www.jtkllc.com and www.jtksolarsolutions.com). He has 10 years of solar washing experience with JTK, as well as five years of experience selling solar washing equipment. In 2015, Koch was a pioneer in addressing the soiling issue for underperforming solar arrays, using cleaning. He had the first company in North America with a robotic solution to clean modules safely and efficiently. Since then, Koch has served hundreds of clients across the U.S. He has also distributed many robotic cleaning solutions all over North America.