With hundreds of residential solar systems on the ground, Power Production Management, Inc. (PPM) is often asked about proper solar panel cleaning methods. Here is what we have to say about solar panel cleaning when it comes to residential solar systems:
1. Do I really need to clean my solar panels? Is the soiling (dirt/pollen) on your panels seasonal or permanent? How heavy is it? If the soiling normally gets washed off with the rain, then it is probably better to wait. The tilt angle of the array often affects the optimal cleaning schedule, as well as pollen seasons. Typically, panels installed at a 22 degree angle or steeper require at least one annual cleaning, if pollen-heavy or dusty geographical regions. However, our customers often find that a light soling may cause a mild reduction of performance that is not significant enough to invest hundreds of dollars to have the modules cleaned. In those cases, it may be feasible to defer the cleaning or choose an altogether less frequent cleaning schedule. Additionally, it is recommended to track the PV system performance to assess the effect of soiling and clearly weigh out the options.
2. I am cleaning my panels and I am doing it myself! Do you have what you need to clean your panels safely and efficiently? Consider the roof access, heights, all other hazards, as well as obtaining proper fall protection. We recommend using an OSHA-compliant fall protection kit (if you must do this yourself and consider doing it on regular basis make sure to properly install (or have a licensed roofer install) a permanent fall protection anchor.
Here is the permanent anchor that PPM uses (we are not affiliated). It works for most shingle roofs, installs very quickly and looks great.
Here are a rope and a harness kit suitable for most residential folks out there with shingle roofs. Solutions are available for all roof types with a quick search online
Here is a highly recommended read published by OSHA regarding solar panel installation and maintenance safety.
3. Additional safety considerations. Always turn your PV system off before cleaning. Water tends to aggravate any insulation issues, which may include ground faults, arcs, damaged modules, (glass, backing, and/or junction box), and many others. Open circuit voltage is always present as long as panels are exposed to light and can cause injury or death. Electric shock considerations should be viewed in the context of a potential fall hazard. After the fall and electrocution considerations are addressed, remain vigilant with respect to personal and personnel safety – use appropriate PPE, and for those of us in warmer climates – stay hydrated and avoid heat stroke.
4. Maintain the module warranty. It is always important to consult the module manufacturer for recommended cleaning method. Surprisingly, we find that recommendations may differ a lot. Some recommend a squeegee, and some strongly advise against it, for example. Most agree that a soft brush, mild soap, and deionized water to prevent streaks are the way to go. The glass coatings and texturing may vary and may require a different approach depending on the manufacturer. Incorrect formulation or application of cleaning agents during cleaning may damage the panels and cause a warranty issue. Another commonly agreed upon rule is not to use any harsh chemicals, including household glass cleaners.
5. Hire a contractor to do it. Now that you are an expert, you can ask your potential contractors all the right questions to determine if they are the ideal candidate to clean your solar system! Make sure to get 3+ quotes, make sure that they are licensed, insured, well-reviewed, and provide access for your contractor of choice to use water and de-energize the system. Don’t forget to compare the solar production before and after the cleaning for your reference!
Good luck – and as always Thank you for being an energy Producer and not just a Consumer. Please be safe.