Why Clean Solar Panels Regularly?

The common mistake in deciding whether or not to clean solar panels, is to base that decision solely on efficiency. One might conclude that since efficiency has not degraded much, cleaning is not really needed. It happens to be though, that efficiency is just 1 out of 4 key reasons to regularly clean panels. I often compare cleaning solar panels with cleaning vehicles. We don't clean our vehicles just once a year, since for me at least, it's about long-term maintenance. It's the same for solar panels, where the hope is that it lasts for 20 or more years.

Regular cleaning can remove dirt and debris that can accelerate oxidation, helping to slow down the process and maintain the appearance of a surface.

One of the key reasons why I hand wash my vehicle versus simply hosing it down, is that soft friction cleaning prevents oxidation from starting. It's the same for solar panels. Regular cleaning can remove dirt and debris that can accelerate oxidation, helping to slow down the process and maintain the appearance of a surface. In the case of solar panels, the effects of oxidation is so profound that one science paper called oxidation "a dominant source for reduced efficiency of silicon solar photovoltaic modules." Of course, how the surface is cleaned is equally as important as the regularity. I don't use automatic car washes because the spinning bristles eat away at the coating. Likewise, there are many wrong ways to clean the solar panel that can do the same.

Oxidation can be seen starting to take hold in the corner of this panel. Oxidation is the leading cause of long-term degradation in efficiency, and regular cleanings go a long way in preventing this

Another key reason why regular cleaning is important is to protect the panel coating. Like vehicles, most panels have a surface coating called ARC, or Anti-Reflective Coating, which also provides a layer of protection from the elements. Once this coating is compromised, oxidation can take hold faster, so preserving this coating is important for longevity. According to John Ibbotson, Consumer Reports’ chief mechanic, regular washing can help protect the vehicle finish, and the same principle applies to solar panels. "You need to remove that grit and residue left from rain and birds, or it can lead to damaged paint and corrosion." The same reference mentions: "Washes keep that grime and dirt from settling into paint. The dirt will actually sweat into the paint, and that detracts from the gloss.” Panels obviously don't have a painted surface, but the point is, they have a coated surface where the dirt can settle into.

Washes keep that grime and dirt from settling

The third key reason to regularly clean, is because the solar manufacturers recommend it. Often we don't know who to trust when it comes to maintenance advice. Usually though, the manufacturer has our best interest in mind, since the longer their product lasts, the more loyalty it builds. Silfab Solar, one of the top solar manufacturers, states this in their maintenance article: "It is advisable, particularly in more arid climates where there is less rainfall, to do cleaning between 2-4 times a year." While efficiency is the official reason to do the cleanings, I suspect the first two reasons play a role in their recommendations.

I suspect the first two reasons play a role in their recommendations

We reach the fourth and most obvious reason to do regular cleanings, and that is to increase efficiency. How much efficiency gained will depend on the factors mentioned above, and how old the panels are, there have been real-world observations such as this one where just in a span of one year and having the panels cleaned, a 36% increase in efficiency was realized. Your mileage will vary of course.

In conclusion, it's not just about the efficiency, although that is an important reason. It's for all these reasons: preventing oxidation, protecting the coating, following manufacturer recommendations, and yes, increased efficiency. Regular cleaning is really about long term maintenance, and we offer high-value 3 and 6 month plans so that the cleaning is affordable!