With grid and electrical service instability happening with nearly every swing in the weather, more and more people are choosing to be self-sufficient with their energy needs and install solar panels. Switching your electricity usage to solar is a good investment, both for the environment and yourself — or at least it can be if your panels are properly maintained and able to operate at peak potential.
Just like everything else, solar panels require a degree of maintenance (albeit a small one). Data shows that solar panels that are maintained with a regular cleaning protocol produce more energy than solar panels where dust and debris build up. But let’s take a closer look at the what and why so we can gain a more thorough understanding.
How Do Solar Panels Work?
To understand if obstruction from dust can affect solar panel output, it helps to understand how solar panels work. We covered the topic in-depth in this article, but a basic explanation is that the black, reflective surface you’d recognize as a solar panel — also known as a photovoltaic cell — is a collection of silicon-based cells that use their surface area to catch photons from sunlight and generate an electric charge. This electric charge is converted to electricity that we use in our homes and other places.
Given that solar panels need unobstructed exposure to sunlight, it makes logical sense that anything that gets in the way could affect their efficiency. That’s why any well-qualified installation company will perform a full site evaluation to make sure that trees, buildings, and anything else will not impede the solar panels’ access to full sunlight during the limited daylight hours.
But besides the obvious fact that a big oak tree throwing shade over your panels will be a major problem, what about pollution, dirt, and dust? Bird droppings? How much do those casual dings from the elements affect the output of your panels? What kind of cleaning regimen is necessary to stay ahead?
Does Cleaning Solar Panels Make a Difference?
Fortunately, the scientific community has devoted significant time and resources to analyzing and optimizing all aspects of solar-generated electricity, including whether cleaning can maintain or improve the function of the solar panels themselves.1 And, consistently, it’s clear that clean solar panels perform better than dirty ones.
The industry even has a term — soiling — which is used to describe the loss of power generation from the accumulation of dirt, dust, bird droppings, and all that other environmental debris that settles on solar panels. And within that definition, dust itself is a broad term that includes any and everything from soil to volcanic ash, sand, clay, pollen, and more. Not only are solar panels exposed to the elements, and they’re also typically more horizontal than vertical. That flat, horizontal surface provides an easy place for dust to land.
One comprehensive review reported a significant number of findings related to the effects of soiling, including a three-month exercise that was done in an industrial area of Boston.1 The test was designed to analyze the effect of dust accumulation on solar panels and it was reported that accumulated dust reduced efficiency from 1 to nearly 5%. Another study out of Tucson evaluated three different soiling situations and found an average reduction of about one percent.2 Still, people in other locations have reported fluctuations of 10 to 20%.3
It really depends where you are at but it’s certain that dirty panels aren’t as efficient as clean panels and that inefficiency compounds every day. Even more interesting is that dirt and dust on the panels affect performance by doing more than simply physically blocking the sunlight. Dust particles don’t settle evenly, and it seems that the uneven spread further impedes the cell’s ability to convert solar energy to electricity:
“Hard dust on a surface of a PV array with a single string will reduce the voltage of the string, but the inverter will detect this reduction and immediately regulate it. However, when there is uneven hard dust on different strings in parallel, a voltage mismatch occurs. In this condition, which is called partial shading, different parallel strings, which are connected to a common inverter, deliver different voltages to the inverter. This makes it difficult for the inverter to seek the optimum point of voltage at which the maximum power is delivered.1“
How to Clean Your Rooftop Solar Panels
Now that we know that solar panel efficiency depends upon unobstructed exposure to sunlight and sediment of any kind — whether it be a downed tree branch or a coating of pollen — will negatively affect solar electricity generation and output, the next question is how to clean them.
The answer is simple — water. Many experts recommend cleaning solar panels with water only, saying that soap leaves a filmy buildup. Check with your installer and the recommendations from your manufacturer. At the very least, avoid detergents and harsh chemicals. There’s nothing to be gained by using something like bleach on your solar panels. If you have bird droppings or something else for which water just isn’t enough, there are a number of products available that are created specifically for cleaning solar panels. Non-abrasive brushes on poles, some with built-in hoses, are affordable and readily available tools of the trade that make the task fast and easy.
You might also wonder if rain is sufficient for rinsing solar panels. The answer is that it can be. Although it’s not always as predictable in frequency, duration, or “cleaning power,” rain provides an organic and welcoming rinse that cleans the surface of PV systems of dust and soil.
If your panels aren’t easily accessible or you’re simply not interested in the chore, outsourcing the work is a cinch. Many companies that provide exterior maintenance are also branching out into solar panel cleaning. If you work with someone who takes care of your yard, gutters, or windows, ask if they also clean solar panels. Most homeowners find that proportionate to the cost of the solar panels, having them regularly cleaned is extremely affordable.
When is It Time for a Cleaning?
The easiest way to determine if it’s time for a cleaning is to simply take a look at the panels. If your natural response is more of a grimace than a feeling of pride, it’s probably time to clean up your panels. Additionally, if you notice that your system’s performance is down, you definitely should include cleaning as a starting point for troubleshooting.
If your system includes micro-inverters with an inverter attached to each panel, it can actually show if a certain area has been covered by bird droppings or other grime. In these situations, you’ll be able to see the lack of flow on the inverter.
Your installation company should also explain cleaning recommendations per the manufacturer’s instructions. Keep in mind that the frequency at which your panels need to be cleaned depends greatly on your location and environment. The composition and concentration of dust vary tremendously from one geographic area to the next, so while some people may need to clean their solar panels every month, others may get by with a biyearly schedule.
Wrapping It Up
Solar systems are often relatively easy to maintain but keeping them clean of dirt, dust, and environmental debris is essential maintenance for ensuring an efficient system that performs for many years. Although self-cleaning robotic systems will likely be the norm in the future, implementing a manual cleaning schedule now is essential for anyone with a solar panel system. Spraying them with the garden hose is a minimal but effective DIY measure that many homeowners take. Others simply contract out the work like any other service and don’t worry about it. Regardless of which approach you choose, keeping your system clean will ensure it performs reliably for the long term.