Solar panel cleaning
Hosing down your solar panels once or twice a year can keep performance high
The number of U.S. households installing solar panels is increasing every year. In 2021, residential solar installation rose by 30% over the previous year, according to the Solar Energy Industries Association. This rapid growth means more homeowners will be maintaining home solar systems soon.
Because of the way solar panels work — by collecting photons from sunshine to convert solar radiation into usable electricity — it’s important that their surfaces remain clean. Any wet leaves, debris or film on the surface of a solar panel can block incoming solar radiation and reduce efficiency.
Key insights
- Not cleaning your solar panels reduces efficiency by 25% to 35%.
- Some areas may require more frequent cleanings to maintain top efficiency.
- DIY solar panel cleaning can lead to an expensive mistake if not done correctly.
- Hiring professional cleaners costs about $150 a visit.
How often should I clean my solar panels?
Most solar panels require at least annual cleaning, though cleaning them more often is not uncommon. “The general rule for solar panel maintenance is to have them cleaned every six months,” says Jesse Silkoff, CEO of MyRoofingPal. “However, if you feel that weather conditions or other factors are dirtying them between cleanings, it might be beneficial to schedule cleaning as often as four times per year.”
Measuring solar panel efficiency is the best way to determine if cleaning is necessary.
Factors that impact the efficiency of solar panels include:
- Weather and climate: In wetter climates, solar panels may only need an annual cleaning — rain does a pretty good job of cleaning dust, pollen and pollution off panels. In dry regions, solar panels should be cleaned more often (at least every six months, depending on how much debris the wind deposits on them).
- Smog and pollution: If smog or pollution is high in your area, clean solar panels as often as monthly. Smog and pollution not only cause deposits on solar panels; the haze in the air will reduce available sunlight to the panels.
- Pollen: Seasonal pollen is common from spring through fall. Clean panels at least every six months in areas of high pollen count.
- Residue from biotic life, including tree sap, pitch and bird droppings: In areas where these are common, remove hard deposits as soon as you see them.
The best way to determine if your solar panels require cleaning is to measure their efficiency. There are smart devices that pair with your solar array to make checking the efficiency of each panel easy and straightforward. The data can also give you a valid picture of the overall performance of your solar array. If you find a drop in efficiency, it’s time for a cleaning.
» LEARN: Solar panel efficiency
What’s the proper way to clean solar panels?
Cleaning your solar panels yourself can save you money, but it’s important to do it the right way. The product manual that came with your panels will outline the best way to clean your specific system. Some manufacturers only recommend using your hose to spray off your solar panels, but your manual may also specify what products to use, what products to avoid and how to protect your system from damage during the cleaning process.
Use water and a very soft material to scrub with. No soaps or anything abrasive. Soaps tend to leave a film and that film is just as bad as the dirt you are trying to remove.”
Following directions is essential. Using incorrect cleaning techniques or abrasive cleaning supplies can result in an expensive problem.
“Use water and a very soft material to scrub with. No soaps or anything abrasive,” advised Scott Briley, managing partner at KC Solar, a panel installer based in the Kansas City area. “Soaps tend to leave a film and that film is just as bad as the dirt you are trying to remove.”
Briley explained that, in general, the most important thing is to be cautious with every step of the cleaning process. Power washers, which most manufacturers don't recommend, can be acceptable if used correctly, he said. “As long as you keep the spray tip at a relatively light level you should be OK,” Briley said. “We do not want to penetrate the surface of the glass, so you do have to be careful with that.”
The best time to clean solar panels is at dawn or dusk — when the amount of sunlight is minimal. If you like to do chores during the day, wait for a cloudy day when incoming solar radiation is weakest. Whatever time of day you clean your solar panels, be sure to power down the solar array before you start.
Are there solar panel cleaning services?
If you don’t want to clean your panels yourself, you can pay professionals to do it.
Before hiring a professional service to clean your solar panels, check your solar contract to see if cleaning is included in your maintenance agreement. Also, read over the warranty for your solar array to see if there are any requirements specified that address who's responsible for solar panel cleaning and what the recommended process is.
Most solar panel installation companies also offer cleaning services, and if they don’t, they might be able to refer you to a company that does.
» MORE: Solar panel installation guide
If you hire the same company that installed your panels to do the cleaning, they’ll probably inspect your system during the process to make sure everything is in working order. This can give you a little peace of mind.
In many cases, a solar company will try to sell you on a regular maintenance and cleaning plan when you purchase your panels. Regular maintenance will keep your panels operating at optimal efficiency, so it’s often worth the cost if you don’t want the hassle of cleaning them yourself.
How much does it cost to clean solar panels?
On average, it costs between $100 and $350 to hire a professional to clean your solar panels. There are a few factors that impact the cost of cleaning solar panels, including:
- Array location: On-ground systems are more affordable to clean than rooftop arrays. Systems that are complicated or even unsafe to get to — for example, if your roof is steep or extremely slanted — may incur increased labor hours.
- Panel size: Smaller systems may be more affordable to have cleaned, though many companies just charge a base fee for all systems.
- Debris: The more buildup there is, the more expensive the cleaning is.
» READ MORE: Cost of solar panels
FAQ
Why isn’t rainwater enough to clean solar panels?
As a general rule, rainwater often is enough to clean solar panels. However, in places where there's not enough rainfall to wash away dust and pollen, the panels will need to be cleaned. Also, when the panels are dirty and the rainfall isn't strong, dirt or pollen can pool and create caked-on mud, which can make the panels less efficient.
Should you avoid soap when cleaning solar panels?
You should always start the process with plain water first to see if that works to clean the panels. If water alone isn't enough, you can generally use a mild soap, but be sure to work in small sections and rinse the soap off quickly.
Dried soap can cause hazing that blocks sunlight. Solar radiation will heat the panels and make the soap dry faster, so it’s best to clean with soap when the temperature is cool — maybe early in the morning. Or you can put it off until fall or winter.
Is it OK to clean solar panels with hard water?
You should avoid the use of hard water when cleaning solar panels. Any scaling — the deposit of mineral residue left on the solar panel — will cause a decrease in the panel's ability to absorb sunlight. Trying to remove mineral deposits from solar panels can damage them.
If you have hard water, it's best to use a cleaning service. A professional cleaning team will have a reservoir of clean, clear water to use under pressure rather than using hard water from your tap or hose. You can do it yourself if you have the right tools to use clean water without minerals, including salts.
Is it OK to power-wash solar panels?
It’s not usually a good idea to power-wash solar panels. High pressure can cause damage to your panels that's expensive to fix. Most manufacturers recommend hosing panels down with low pressure.
Can you walk on a solar panel?
Walking on a solar panel isn’t recommended. Pressure can lead to cracks in the panels, and damage caused by walking on the panels may even void the warranty. Also, debris from your shoes can undermine the panels’ efficiency.
Bottom line
Solar panels are a great investment for homeowners interested in sustainability. Although they’re inherently low-maintenance, they do require some cleaning to ensure the highest level of efficiency and output. Regularly checking your panels to see if they need cleaning is a good way to keep your panels working properly.
Cleaning solar panels can be a DIY job, but be sure to follow the manufacturer’s cleaning instructions. If you can’t or don’t want to clean them yourself, there are professional cleaning companies with the tools and skills to get the job done safely and correctly. Just make sure to choose a company that's licensed to operate in your area if necessary, and check its references and insurance.
Article sources
- Solar Energy Industries Association, “ Solar Industry Research Data .” Accessed May 26, 2022.
- Popular Mechanics, “ Pollution Could Block 25 Percent of the Light That Would Become Solar Power .” Accessed May 26, 2022.
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