How to Keep Your Solar Panels Clean

Dirty solar panels can result in up to a 25 percent decrease in energy production.

Where every kilowatt makes a difference in your home's energy production and use, that's a significant loss. 

When you purchase solar, the estimated output of a particular solar system takes into account "unavoidable losses due to soiling." In an attempt to compensate for the production loss, many solar owners resort to adding more panels to their system later on, when the problem could be aided, in part, by keeping panels consistently clean.

We'll walk you through the "why" and the "how" of solar panel cleaning so you can determine the best course of action for maximizing panel efficiency while protecting your investment. 

Do I need to clean my panels? 

Your location, terrain, and weather conditions will determine the frequency of solar panel cleaning. If you live in a desert, a wooded area, or a highly-polluted area, you'll need to be more proactive in your approach. 

But before you do anything, contact your solar company to see if your contract specifies any cleaning or maintenance benefits. If you lease your solar panels, the solar company that owns them should be cleaning and maintaining the panels at no cost to you. 

What is making my solar panels dirty? 

Soiling comes in many forms:

• Bird droppings
• Pollution grime
• Dirt
• Dust
• Ash from wildfires 
• Pollen
• Fallen leaves
• Ocean salt 

When these materials cover your panels, it makes it harder for the particles of light to reach the panels, preventing the solar cell technology from working at optimal efficiency.

If you don't currently clean your panels or only do so once or twice a year, you may want to consider doing more. 

Will rain keep my panels clean? 

A common misconception is that the occasional rainfall is enough to clean your dirty panels.

Heavy rain can indeed be effective in clearing off your panels, especially if it's frequent.

Light rain, however, can be even worse than no rain, because instead of cleaning the panels, it enables dirt and dust to harden on them. Additionally, rain can bring with it pollen, which can soil your panels. 

Which cleaning method is the best?

There are certain things to be mindful of to make sure the cleaning method you choose will not harm your panels or void your warranty. As you consider your options, aim for a solution that will increase panel productivity without costing more than the value of the extra energy production you're benefitting from as a solar-power-generating household. 

DIY (Do-it-yourself) 

The most important point we want to make in regards to DIY cleaning is to consult your solar contract, warranty, and manufacturer instructions prior to attempting this on your own. The last thing you want to do while trying to save money is to void your warranty. 

You'll want to keep these other tips in mind: 

• Power off—Solar panels should not be cleaned while active, so check your manufacturer's specifications for turning off the electrical currents produced by the panels and going into your home. 
• Scaling your roof—Climbing up onto your house can be dangerous depending on the height and angle of your roof, so use the appropriate ladder size and gear and exercise caution if you proceed.
• Water—Cleaning solar panels the correct way requires using soft water to avoid lime-scale buildup that can damage the panels. You can treat your hose water with a water softener if it's hard water. Deionized or distilled water works best as you treat your panels with a mild and non-abrasive detergent, vinegar, or solar-panel-specific cleaning solution. 
• Scrubbing—Using hard brushes can damage your panels, so use a soft scrubber or dishcloth instead. 
• Temperature—If you rinse panels with cold water on a hot day, the glass of the panels may crack as the water dries, so cooler days are better to minimize this risk. 

Professional cleaning services

You can avoid the hassle and risks of roof-climbing and DIY cleaning by hiring out this task a few times a year. That way, you can trust that the water has been treated appropriately and the job was done efficiently.

However, the obvious downside here is cost. Depending on the frequency of cleaning, you might spend more money on cleaning than the money you're saving by utilizing solar power over grid-generated power. 

You can check Thumbtack's average cost calculator to find solar panel cleaning costs nationwide and to shop out specific solar panel cleaners in your area. The average tends to fall between $100-200 per cleaning, though this can vary based on the size of your panel array and your city. 

Automated cleaning systems

Installing an automated cleaning system is a good choice if you're looking for a permanent solution to solar panel cleaning and you can afford yet another investment in your solar system. 

An automated system reduces the risks of 1) damaging your panels with manual cleaners, 2) injury from falling off of your roof, and 3) losing significant solar power from turning off your system for large-scale cleanings. Additionally, a cleaning system can be eligible for the 30 percent federal tax incentive when purchased with a new solar panel system (consult a tax professional for guidance regarding your eligibility for federal and state tax incentives). 

Products and systems vary by brand, but automated solar panel cleaning systems generally include a nozzle permanently affixed to the roof or panels. The connected housing system is located on the ground and includes the soap, water, and anything else necessary to operate the system. 

One such system, RST CleanTech Solutions, uses technology that keeps panels consistently clean with only minimal use of water and no soap. Aside from a yearly filter change, the system doesn’t require maintenance and it can be controlled by an app. 

Control what you can 

Solar cell efficiency inevitably decreases over the lifetime of a panel. That's why manufacturer warranties for solar panels and solar roofs are in the 25-year range. 

But cleaning the surface of your solar panels is something you can do to make the most of panel productivity over time.