The cleaning conversation

We know that for many companies that install rooftop solar panels, keeping them well-maintained is a subject that many installers don’t concern themselves with.  Some solar installation companies do instruct their customers on maintenance but in our conversations with installers and rooftop solar owners, this conversation is brief. 

What happens to solar panels when they get dirty?

There is no shortage of natural factors that will cause accumulation on solar panels: 

• Dust
• Pollen
• Bird droppings
• Tree sap
• Soot
• Sand (especially in areas close to agricultural areas). 

All of these particles sink in the air around us and come to rest on your solar panels. And that's not all: moisture accumulates at night, eventually condensing into droplets, and the more flat, even and smooth the surface is - the more the moisture just sits there. This accumulated moisture combines with all those particles we mentioned before and creates a heavy mud, just like dough or cement, which wind or rain cannot remove. Night after night, the moisture in the air makes the paste stickier, attracting more dust, pollen and sand, encouraging the layer to settle in a thick layer on the surface of the panel.  In short, this dirt is here to stay, unless you take care to clean it!

Tip

Isn’t rain enough to clean my solar panels?

One of the myths (that should be debunked!) is that the rain will do its work, and the panels will be cleaned from season to season.   We know this isn’t actually true, and this 2023 study on Clean Technica has also debunked the myth that rain will keep panels clean.  So, why doesn’t rain clean solar panels? First of all, in the sunniest parts of the US such as in the states of Arizona, New Mexico, Nevada, California, or Texas, the rain is insufficient to clean the panels thoroughly or frequently enough. In addition, rain can only reduce fine dust - but not coarse dust, sand, pollen, triple ions and dirt that crystallizes during dry periods on the panels.  Also, the relatively flat angle at which the panels are installed in most home systems only adds to the accumulation of dirt. So, while rain can remove loose dirt, it's not a substitute for a proper cleaning method to get rid of persistent pollutants like pollen. 

How do you clean your own solar panels?

Facts are facts: 13 billion paper towels are used annually in just the United States, adding to an already unmanageable amount of waste in landfills, oceans, rivers and lakes.

As a conscientious consumer invested in solar energy, you don’t make a decision just for your personal well-being; it's a commitment to the health of our environment and the sustainability of our communities. Instead of adding to the problem of excess waste, when you clean your solar panels, use a method that is 100% reusable with zero waste per use.

The problem with tap water, a squeegee, and soap

There is no doubt that as fellow DIYers, we always look for the quick solution.  Why not just go up to the roof with a rag and a hose?  But in reality, washing without proper knowledge and equipment can cause heavy damage to the system. (Remember that warranty?) These damages may not be visible at first, but over time affect the efficiency and the panels dramatically. This is where using the right tools and techniques come in. View our comparison chart of some common methods used to clean panels.

Protecting your solar panel warranty is crucial to ensuring the long-term performance and reliability of your investment.

The most important factor in keeping your warranty intact is regular maintenance, and safe, routine cleaning is number one on the list of maintenance checks. However, accidental damage like scratches or degradation of the anti-reflective coating caused by using unapproved cleaning methods will most likely void your warranty, leaving you financially exposed if a repair is needed.

The dangers of dirty solar panels

How does dirt damage a solar panel?   A little dirt can become a lot of dirt fairly quickly, and the efficiency of solar panels depends on how much they are exposed to the sun: dirt literally gets in the way of efficient energy production.  But this is not the only problem.  There is a much more serious problem: long-standing or permanent dirt creates hot spots on the panels - and these cause the system to overheat. How does that happen?  As soon as dirt accumulates on one part of the solar panel, sunlight does not reach the photovoltaic cell below it - compromising its function.  Consequently, the load on the other PV cells connected to it increases - and the entire system heats up as a result. The reduced capacity of the blocked cell causes it to resist the passage of current through it, which causes accelerated wear and tear of not only the cell but also the materials around it.   Eventually, it will stop working. The efficiency of a system that is not regularly maintained can drop by about 30%, and produce electricity inconsistently and inefficiently. Not only does the efficiency of the system decrease as soon as it heats up, consistent overheating over time can cause the entire system to stop working, as well as causing other damages that are not covered by the manufacturer's warranty.

1. Effectiveness at removing dust and debris

Dirty solar panels produce less energy. For the most sunlight absorption and energy production, a clean panel needs to be 100% clean. Any leftover dust can get caked on in layers that become nearly impossible to remove and block light absorption. Long-term, this leads to hotspots and eventual cell failure, or worse, possible system failure.

Are your cleaning tools merely pushing dust around? Or are they really cleaning the surface and allowing the PV cells to absorb the most light?

2. Leaves no hard water spots or residue

There are two main sources of residue or spots on solar panels. One is the water itself that is used to wash the panel. Terrible irony, there. Tap water right out of your home’s main water line will eventually damage the solar panel because it contains heavy metals and salts. Over time, built up mineral ions reduce solar cell performance, create hot spots, and negatively affect your panel's effectiveness by as much as 30%!

The second source of residue is that which is left by cleaning solvents, soap, or other solutions. The time it takes for water evaporation to occur is just seconds, leaving behind foaming agents, oils, and other unwanted substances on the surface of your panel.

3. Does not use detergents or skin irritants

Do you pat yourself on the back for using only “natural” soaps and cleaners, and think they would be safe to use on your solar panels? What does “natural” mean, anyway? Welp, when it comes to the advertising and marketing of cleaning solutions, it doesn’t mean much. According to the Environmental Protection Agency’s FAQ: “Cleaning products marketed as “natural” typically use chemicals made from corn or other biological sources, rather than petroleum. While these cleaning products may be made out of renewable resources, their “natural” ingredients are still chemically identical to those made from petroleum, so their potential health and environmental impacts during and after use would be the same.” (https://www.epa.gov/saferchoice/frequently-asked-questions-safer-choice#pane-10)

Can you trust a pro to use a safe method to clean your panels? The jury is out, considering a basic Google search will bring up a variety of “professional” cleaning solutions sold by the gallon. Just because it’s blue doesn’t mean it’s true. The truth is that the only safe panel cleaning solution out there is deionized water, like the water produced by the SolarWater™ capsules.

4. Environment and wildlife safe

Facts are facts: 13 billion paper towels are used annually in just the United States, adding to an already unmanageable amount of waste in landfills, oceans, rivers and lakes.

As a conscientious consumer invested in solar energy, you don’t make a decision just for your personal well-being; it's a commitment to the health of our environment and the sustainability of our communities. Instead of adding to the problem of excess waste, when you clean your solar panels, use a method that is 100% reusable with zero waste per use.

5. Protects solar panel warranty

Protecting your solar panel warranty is crucial to ensuring the long-term performance and reliability of your investment.

The most important factor in keeping your warranty intact is regular maintenance, and safe, routine cleaning is number one on the list of maintenance checks. However, accidental damage like scratches or degradation of the anti-reflective coating caused by using unapproved cleaning methods will most likely void your warranty, leaving you financially exposed if a repair is needed.

6. Simple to store at home

Among the cleaning methods we researched, the simplest tools were the easiest to store, for the reason that items such as paper towels, a squeegee, or cleaning spray already have a place for storage under a sink, and a hose is usually already hooked up and ready for use. Using a professional service is even simpler, because they bring their own equipment and take it with them when they go. ​

The SolaReef Cleaning System can be stored (without being attached to a water supply) much like a broom, hanging on a wall rack or hook with the brush facing the wall to protect the bristles. We like this solution that creates a wall storage solution anywhere in the home or garage.

7. Ergonomic and quick to set up

Whether you are cleaning your panels yourself or hiring an outside team to come to your home, ease-of-use and time definitely matter.

When you hire a guy, you have to book the appointment so that sometime next month, a truck will show up late. The process of positioning the truck just right in your driveway, attaching hoses, accessing your roof, cleaning your panels, then dismantling the whole thing can take hours, while you stand and watch to make sure they don’t knock off roof tiles or take long breaks. If you are like us and want to DIY, but you’re cleaning your panels using a hose and untreated water, you have to race to dry the panels before they dry covered in spots from the minerals in the water. Aching arms AND spotty panels? No thanks. SolaReef solves the two important issues of time and ease-of-use. First, you don’t need to hire a guy. You want your panels cleaned today because of some serious dust? Hook SolaReef up and get to it. The extendable pole is ergonomically designed to distribute weight in a way that makes it easy to use even when fully extended. The brush literally does the washing and wiping for you. As for the race to dry before spotting, when you use the deionized water from the SolarWater capsules, there are no minerals to wipe off. In fact, you can leave your panels to dry in the open air, saving you time (and delayed onset muscle soreness).

8. Won’t damage PV cells or other structures

If you haven’t already figured it out, there are many ways to scratch your panels, specifically the anti-reflective coating, or ARC, that functions to absorb as much sunlight as possible. Squeegees, paper towels, scrubbing brushes that work great at removing soap scum? Not for your panels, please. All of these common cleaning tools are too abrasive, and not designed or recommended for solar panels.

A professional may use a good quality brush. You should definitely ask. But many of the brushes we’ve tested on panels during the development of the SolaReef200™ solar panel brush were still too tough, and didn’t have any built-in protection against dings and dents to the panel system.  

9. Affordable

Many of the cleaning methods listed in this article are cheap and affordable, while others cost more. From the get-go, the goal of cleaning your panels is to maintain them and keep them operating at their max to save you more money, so why risk damaging them in the process? On the other hand, hiring a professional cleaning service ensures a thorough, safe clean with minimal effort on your part. However, this is the most expensive option and might not be necessary unless your panels are particularly dirty or difficult to access.

More expensive upfront than some of the other methods, yet hundreds less than a professional service, theSolaReef system could save you money in the long run by preventing damage to your panels and maintaining their performance.