The appearance of any unknown substance on your solar panels can be a cause for concern. One of our customers recently contacted us about a dusting of white powder they saw on their panels. Our examination revealed that the culprit was pollen that had accumulated on the solar panels, so there was no reason to panic, as the panels were still producing energy, they just needed a good cleaning.
We suggested that they could start by spraying the pollen off using a water hose to clean the panels. Then we recommended that they sign up for a thorough panel cleaning service at least once per year. It would prevent build-up in the future and ensure maximum efficiency and savings from their solar power system.
This homeowner’s concerns got us thinking about the sort of solar panel cleaning questions that most homeowners have:
- Do solar panels need cleaning?
- What solar power cleaning tasks can you do on your own?
- When should you hire a professional cleaning company to clean your solar panels?
- Will cleaning your solar panels improve their performance?
This article will answer all your concerns regarding these and other questions.
What are the Causes of Dirty Solar Panels?
You need to oil, maintain, and clean your car so it runs more efficiently. Others want their house windows to be crystal-clear and grime-free so they can enjoy the view of their property. For many of the same reasons, your solar panels also need cleaning. Accumulated leaves, bird droppings, and other debris can block a significant amount of the sun’s rays, reducing your system's efficiency.
We all love trees, as they beautify and freshen up our property. But birds also love them for nesting or chilling spots. If branches hang over your solar panel array, you should be prepared to do some extra cleaning.
Bird droppings tend to be more notorious than dust, leaves, and pollen, especially if they harden and stick on the panels. The accumulated debris from birds can block significant light from the sun, and it’s more difficult to remove just by spraying your panels with water.
Thankfully, products and services exist that can indicate if bird droppings affect the current flow in your solar energy system. Microinverters help with this, as the technology allows you to see when a single panel is generating less electricity because of blockage or debris.
Pollen and Leaves
Pollen has evolved into a sticky material that doesn't dissolve in water. As a result, it can be harder to clean since it doesn't just blow away in the wind. If you live near farmlands or areas with a lot of vegitation, expect pollination agents like wind, insects, and birds carrying pollen to pass over your panels and drop some of it on them. In fact, windy weather is more likely to blow pollen onto your panels in the first place instead of blowing it away.
You may also need to deal with leaves falling on your panels, especially if your trees are deciduous, meaning they lose their leaves each year in the fall. While dry leaves just blow away in the wind, wet leaves typically stick to panels as heavy rain can act like glue.
Dust and Dirt
Dust and dirt is a common enemy of solar power systems, and its effects go beyond the accumulation of grime. It’s true that sun rays may still pass through a thin layer of dust, and wind or rainwater can quickly sweep most of it off. But if your PV array is located near dustier areas such as farmlands, main roads, cement factories, and quarries, the story changes. Your solar panels will need special attention and frequent cleaning as they have to contend with far more dust and dirt.
Now, you may be thinking, “Wait. You told that customer to use water to clean their panels. Why is it on the list?”
Fair question! The issue has to do with the pooling of cleaning or rainwater on horizontal solar arrays. Apart from simply reducing your solar energy generation, the water layer can leave a muddy residue after evaporation, necessitating more frequent cleaning.
Do Solar Panels Need Cleaning?
Like anything that stays outside every day and night, solar panels will eventually accumulate dirt. But how frequently you may have to wash your panels depends on several factors, including:
- System design
- Installation angle(s)
- Size/number of panels
- Types of dirt
- Duration between thorough cleanings
So, do solar panels need cleaning? Our definitive answer comes in three parts:
Answer #1: Yes, and You Can Do It Yourself
Bird droppings and other dirt agents can affect your solar panel's performance, especially if your panels lie truly horizontal on the roof. That's where washing the panels becomes important, though it doesn't have to be a thorough or routine cleaning in many cases.
As we suggested to the customer with the white powder on their panels, cleaning your solar panels is usually a relatively easy task. All you need to do is to spray the panels with average-pressure water from a well-angled garden hose while standing on the ground.
If you want extra cleaning power, a long-handled squeegee or soft brush plus a medium-pressure hose nozzle can work wonders. With the nozzle, directing the spray will become easier. You'll then wipe off the water using the squeegee for maximum electricity production. This approach provides even more cleaning power, but it does depend on the angle of your roof, roof height, and panel placement, because not everyone will be able to reach their roof, even with a long handle.
Answer #2: Yes, but You Don't Need to Do Anything
Maintaining your panels is essential, but you don't need to clean them as often as most people think. You may need to remove the occasional buildup of leaves, bird droppings, and other debris to maximize the amount of sunlight exposure your panels receive. Any regular wind and rain will typically sweep off most of the dirt, so it's better to let nature take its course and only do one thorough cleaning every year to maximize energy production.
When it comes to doing any thorough cleaning and maintenance, it’s best to hire a professional with the knowledge and tools to get the job done safely and correctly the first time.
Answer #3: No, Unless Something Really Bad Happens
Researchers at the University of California left solar panels on a roof for 145 days without cleaning. Their findings? The panels' energy generation efficiency dropped by 7.4%.
It may surprise you that the efficiency of your solar panels can remain intact over a long period, considering all that exposure to debris, dust, heat, and rainwater. But you can trust your panels to withstand the regular wear and tear of the elements.
Solar companies employ only the leading technologies and engineering skills when manufacturing their products. Their design processes usually account for the effects of dirt, water, and pollen from everyday use.
You still need to be on the lookout for any obvious structural issues with the panels, supports, and roofing.
Can Cleaning Solar Panels Improve the Performance of PV Systems?
As we've seen so far, the short answer is, "The impact of dirty solar panels on solar power production depends on various factors." But we're interested in the long answer, right? Let’s dig into the science and math a bit:
An experiment involving solar panels on a low-slope roof sought out the difference in energy output before and after a thorough cleaning.
The researchers found an average 3.5% boost in energy production (the amount of power produced over time) after cleaning the panels using a soft rag and water. The implication here is that the energy yield increase was low, despite the high amount of dirt accumulation.
Things became interesting when heavy rain did the cleaning job. The average performance increased by only 1.9% after rainwater pounded on the dirty panels. What does that mean? A good shower from the skies can take care of some cleanup, but it’s not as effective as the proper equipment and some elbow grease.
You may want to check how much your dirty solar panels are costing you in terms of energy generation. Here's a simple formula for determining the value of solar panel cleaning:
Yearly Energy Production (kWh) × Production Loss From Dirty Panels × Electricity Cost per kWh
For example, if your residential solar energy system can produce 10,000 kWh of electricity per year, and you assume a 5% loss of production due to panels being dirty, and you pay $.20 cents per kWh for electricity from your utility, your yearly cost of electricity loss from dirty panels is as follows:
10,000 × .05 × .20 = $100
A 5% electricity production loss might not sound like a lot, but it can definitely add up, and suddenly you’re paying way more to your utility company on your electricity bill than you need to be.
The Science of Cleaning Your Solar Panels
Yes, rain helps wash solar panels and keep dirt at bay, but it comes with several downsides, which can lead to noticeable performance problems on panels set at low angles:
- Rainwater comes laden with pollen and dirt
- It can pool on the surface of your panels, especially if the glass surface sits lower than the frame
- Once the rainwater evaporates, it can leave behind a muddy residue
So, should we rule out the need for cleaning solar panels? Not yet. Researchers at Google's solar farm have a different story.
In one set of their experiments, they studied 1.6MW of horizontal solar panels on flat carports in Mountain View, California. These panels operated untouched for 15 months.
After cleaning them, they realized that the energy production from their carport solar panels had doubled overnight! Eight months later, they cleaned those same solar panels and learned that the output had gone up by 36%.
So, what's our conclusion? All solar panels still need frequent cleaning, especially if they're horizontal or almost horizontal on your roof. If yours are tilted appropriately, a reasonable amount of rainfall will get them mostly clean, but a scheduled annual visit from cleaning professionals may further help your overall renewable energy output.
How Can I Clean My Solar Panels?
Cleaning your solar panels doesn't have to be extensive or risky work. If you’ve decided to clean your panels yourself, what matters is that you follow these cleaning tips to keep both you and the solar system safe.
When in doubt, just remember that you can always call in the professionals to get the job done safely and efficiently. Because some solar installers are only focused on new installations, they don’t all offer services like solar panel cleaning. If that’s the case, rest assured that Palmetto can still provide any of your solar service and maintenance needs.
Tips for Cleaning My Solar Panels
Before setting out to clean your panels, you must keep in mind one crucial point: Avoid scratching or damaging the glass at all costs. You don't want your energy production to plummet.
When cleaning solar panels, you will always be gentle with them by using these solar panel cleaning tips and tricks:
- Solar panel models are not all created the same. It's prudent to check with your product's manufacturer to see if they have specific instructions for cleaning.
- Consider using a garden hose first. But if grime and dirt have built up on your equipment, it's time for a thorough cleaning.
- Most likely, the only equipment you need is a bucket with clean, warm water, a soft cloth, dish soap, and a soft brush or squeegee.
- Pick an evening, a morning, or a cool day to do the cleaning. You don't want to get burned by hot panels on a sunny day. If it’s too sunny, the soapy water can evaporate before you get time to wipe it away, which can leave a smear or residue that can reduce your panels' efficiency.
- Avoid splashing cold water on a hot glass surface. It can lead to cracks due to sudden contraction.
- Apply the warm water and dish soap on the panels' surfaces using a soft cloth or sponge. Do NOT clean the wiring underneath.
- Use a squeegee to get rid of dirty water.
- Never step on your panels, as this can damage them and cause premature failure.
- Avoid brushes with sharp bristles that can scratch your solar glass surface.
If you live near an airport or a route frequented by trucks, expect to find a few oily stains on your panels. In this case, you can use a rag and a little isopropyl alcohol to remove them.
Pro Tip: Strong cleaning fluids should not touch your expensive investment at all. Harsh chemicals and liquids like laundry detergents, ammonia, and acids can react with or streak the glass surface, leading to damages and a loss of energy production.
How Often Should I Clean My Solar Panels?
In most cases, you only need to clean your solar panels once or twice per year. We recommend scheduling your annual cleaning routine during the spring. That avoids the heat of summer and harsh elements of winter.
However, your solar panels might need extra attention in some locations. For example, the Southwest US experiences more significant dirt accumulation because of limited rainfall. Also, panels in homes near airports, factories, freeways, and other sources of pollution will need more frequent cleaning.
Winter and autumn are other special cases. Removing heavier-than-average snowfall and leaves can boost your solar performance significantly.
Do I Clean Off Snow?
We get it - heavy snowfall days can make anyone nervous about their system not generating enough energy. However, snow on your solar power panels usually melts away quickly, thanks to the heat created by the solar panels, and their slick surface. Snow on a panel melts faster than on an empty roof due to the high difference in heat between the two surfaces.
But if the snow is taking longer to melt and your battery storage is running low, you don’t have to wait. You can brush the snow off your panels to get them back to producing power right away.
Make sure you use the right equipment to avoid damaging your investment and compromising its warranty. Thus, shovels, standard brooms, and other non-specialized tools should not come anywhere near your panels. A suitable snow roof rake created for the task will come in handy here. They typically cost around $30 to $150.
Can I Use a Pressure Washer When Cleaning My Solar Panels?
No. Not at all. High-pressure water is among the biggest enemies of your solar equipment.
First, high-speed moisture can quickly force its way through the seals around the frames and get into vulnerable technology. These water leakages can promote corrosion of the fine wires, which leads to the failure of the solar panel and its photovoltaic cells.
Also, the glass surface can break under high water pressure. We hear you asking, "Why then don't we see damage resulting from continuous rainfall pounding on the glass?" That’s because panels are designed to resist hours of heavy rain falling across a wide surface area. But washing the panels with high pressure directs a focused beam of water in a highly concentrated spot, which creates an increased chance of stressed areas that can crack.
What is Localized Soiling?
Localized soiling of solar panels is when material like bird poop, leaves, and any other heavy blockages get stuck on your panels, but only cover part of the panel. Compare that to general soiling, where material like dirt and dust covers the entire panel surface.
When rain and wind fail to remove localized soiling, this sort of debris may block some parts of the equipment, leading to hot spots.
Your panel is made of several individual cells (60 in most cases). When localized soiling blocks sunlight from reaching one of the cells, its energy production drops. However, full current flowing from the adjacent cells may pass through the affected one. The result is overheating at that cell, a phenomenon that can cause damage to the panel.
Yes, modern solar panels come with multiple built-in bypass diodes to keep hot spots at bay. But those extra-dirty areas can still lead to damage over time that can increase your solar panel maintenance cost.
- It's understandable to want to clean solar panels to maximize their performance.
- It's good to pay attention to the condition of your solar panels.
- Be careful with how you clean them.
- Proper cleaning in the right context can improve the performance of your solar panels.
- Deep solar panel cleaning is best left to professionals like Palmetto that have the knowledge, experience, and equipment to get the job done safely the first time.