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Guide to Solar Panel Cleaning Through the Seasons

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Cleaning solar panels with soapy water and squeegee
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Solar panels can provide electricity for decades, and they have few maintenance needs compared with other energy generation systems. However, regular solar panel cleaning is important to ensure they remain productive. When dust and debris accumulate on the surface of photovoltaic cells, they block sunlight, and less electricity is produced.

The best solar panels come with a power production warranty of 25 to 30 years. Like any device, they lose performance capacity over time. High-quality modules will only lose around 0.5% of their capacity each year, but this is only true for solar panels that are cleaned regularly. According to the National Renewable Energy Laboratory, soiling can reduce panels' annual electricity output by up to 7% in some parts of the U.S.

Rain can naturally wash away dirt and particles from the surface of solar panels, especially if they are tilted. So if you live in a place with regular rainfall, your panels will be less affected by soiling. However, solar panel cleaning services are still recommended two to four times per year to make sure your system stays productive.


Recommended Solar Panel Cleaning Schedule

Solar panels are exposed to dust, dirt and bird droppings all year long. Depending on where you live, there may also be seasonal issues that affect panels, and you must make sure these are handled properly. Below are our solar panel cleaning tips for each part of the year.

Fall

As you might guess, a large amount of falling leaves can block a lot of sunlight if you let them accumulate on your solar panels. However, even a small number of leaves can have a major impact on power generation, due to how solar panels work:

  • The photovoltaic cells that make up a panel are wired in series. When even one cell is covered completely by a leaf, the entire panel becomes less productive.
  • Consider that the solar panels themselves are also wired together in strings (series circuits) and connected to an inverter. If one panel in the circuit has issues, all others will be affected.
  • As a result, a single large leaf can affect an entire row of panels if it fully covers one solar cell. As more leaves accumulate, the electricity output continues to drop.

You can clean the leaves on your own, but you should get a rake that is specifically designed for solar panels. Otherwise, you can damage the surface of the solar panels, and your manufacturer warranty may be voided due to rough handling.

Winter

Snow and ice become the main issue for solar panels when the winter arrives. Most high-quality modules have low temperature ratings and will not be damaged by cold weather, but a thick layer of snow can block sunlight and stop electricity production.

  • Snow should be cleaned from solar panels and other roof surfaces as soon as possible.
  • Otherwise, the snow can melt and freeze back into ice, which is more difficult to remove.

The sun can help you by melting some of the snow and ice on your roof, but solar panel cleaning might still be necessary after a heavy snowfall. Again, you will need a specialized solar panel snow rake. Avoid ice scrapers and any other tools that may scratch or damage solar cells.

Spring

There is plenty of pollen in the air during spring, and it can accumulate on solar panels and lower energy production. Regular washing is recommended during this season to prevent pollen buildup. If you're not sure how much pollen you're expected to get, many weather forecasts provide information on pollen levels, and there are also online resources where you can check pollen counts for your zip code.

Pollen allergies are very common, and they tend to worsen during spring. If you or someone else in your home is sensitive to pollen, you might prefer to hire a solar panel cleaning service to avoid direct exposure.

Summer

During summer, the cleaning needs of solar panels will depend on your climate and weather conditions:

  • In regions that get plenty of rain during summer (hurricane season), there is little need to clean your panels because the weather will do the job for you.
  • Regions with less rainfall tend to be hot and dry during summer (fire season), and regular maintenance may be necessary to remove extra dust, ash and other particles.

Solar panels can achieve their highest electricity savings during summer, since there are more hours of sunlight per day. However, this is only true when they are kept clean of grime. Dirty solar panels will always have a lower energy output, no matter the season.

How to Clean Solar Panels

Cleaning solar panels on your own can be dangerous — especially if they are installed on a hard-to-access roof area. In these cases, paying for a solar panel cleaning service is a safer option.

  • Many of the best solar companies offer cleaning services. Some local solar installers may even offer free cleaning for a limited time after your purchase.
  • You can also get in touch with professional cleaners who specialize in solar panel maintenance.

Another option to keep your solar panels clean is installing a sprinkler system like that from Heliotex. These remove dust and other particles automatically. With this type of system, solar panels can also be cleaned more frequently, as nobody needs to climb on your roof. With no chance for dust to accumulate, you generate more kilowatt-hours of energy over time and your power bill savings are higher, lowering your overall solar panel payback period.

DIY Solar Panel Cleaning

Cleaning solar panels on your own is also an option, especially if you have a ground-mounted solar system that you can reach easily. However, you must make sure the panels are not damaged while taking all the necessary precautions to avoid accidents.

To clean your solar panels without damaging them, take note of the following recommendations:

  • Use soapy water, avoiding harsh chemicals. Something as simple as diluted biodegradable soap should do the job.
  • Use a non-abrasive sponge or a soft brush and squeegee.
  • Use a standard garden hose, since a pressure washer can damage your solar panels.

To keep yourself safe, be extra careful when cleaning a rooftop solar system, especially if you have a high-pitched roof. We recommend wearing personal protective equipment including a hardhat and safety harness at the bare minimum.

Also, make sure you stay hydrated while cleaning your solar panels, and avoid working in extreme heat. The risk of heatstroke should not be underestimated, and you will need emergency medical attention if it happens to you. Early morning and evening are the best times of the day for solar panel cleaning, or you can wait to wash your solar panels on a cloudy day.

Cost of Solar Panel Cleaning Services

Solar panel cleaning companies normally either charge per module or charge a flat rate for the entire array. You can expect to pay between $5 and $10 per panel, or $150 to $200 for the entire system, though prices may vary depending on location, season and other factors.

If you don't have solar panels yet, some installers may offer free cleaning for a limited time after your purchase. However, this shouldn't be the main factor when choosing your solar provider. Free cleaning is a nice perk, but make sure you're actually getting a high-quality installation.

How to Tell When Your Solar Panels Need Maintenance

As mentioned above, solar panels are very durable and 25- to-30 year warranties are standard in the industry. However, solar power systems are only productive when their surface is kept clean. Dust, particles and objects will not cause permanent damage, but their electricity output can be reduced drastically.

If your solar panels are producing less electricity than usual, even with sunny weather, they could need cleaning or maintenance. There are two main ways to detect electricity production issues:

  • Many solar inverters now come with energy monitoring apps, and you can simply check the electricity production with your smartphone. If there is a significant drop in the daily kilowatt-hour output, the app will let you know.
  • When your solar panels are producing less electricity, there will also be an impact on your electricity bill. You will notice that more kilowatt-hours are consumed from the grid, which means you pay a higher bill.

Checking your energy monitoring app regularly is a good habit when you have solar panels. You can detect issues faster and get them fixed, instead of waiting for the next power bill. By then, you will have already used a lot of electricity from the grid.

FAQ: Solar Panel Cleaning

Do solar panels need to be cleaned?

Yes, solar panels need regular cleaning, ideally two to four times per year. They are only productive when sunlight reaches their solar cells, and anything that blocks sunlight reduces their output. This includes dust, dirt, pollen, leaves, snow, ice, bird droppings and any other particles or objects that remain on their surface.

What should I use to clean solar panels?

To clean solar panels, you should use a cleaning method that will not damage the cells. Solar panels should be washed with soapy water and a non-abrasive sponge, or a soft brush and squeegee. If you need to remove leaves or snow, look for a specialized solar panel rake and avoid any cleaning tools that could scratch their surface. An easier and safer option is hiring a professional solar panel cleaning company.

Does cleaning your solar panels make a difference?

Yes, cleaning your solar panels has a major impact on panel productivity. According to NREL, soiling can reduce the annual output of your solar panels by up to 7%.

How much does it cost to hire someone to clean solar panels?

When hiring a solar panel cleaning service for your home energy system, you can expect to pay around $5 to $10 per panel or a flat fee of $150 to $200.

Leonardo David is an electromechanical engineer, MBA, energy consultant and technical writer. His energy-efficiency and solar consulting experience covers sectors including banking, textile manufacturing, plastics processing, pharmaceutics, education, food processing, fast food, real estate and retail. He has also been writing articles about energy and engineering topics since 2015.

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