Solar panel cleaning is a hotly debated topic, with many contradictory assertions and claims. The following is not intended to be the definitive “last word” on the issue. These are our general guidelines that we have learned over time, and we present them here as a public service regarding solar panel maintenance.
AM Solar’s 7-point guide to cleaning your solar panels after installation
1. The first thing to remember is that you don’t generally need to clean your panels unless there is an obvious obstruction preventing sunlight from reaching the cells. In our experience, even dusty or dirty solar panels only lose around 10% production on average. If it rains more than a few times a year where you are (or where you travel), you don’t have to worry about regular cleaning in most cases. This is especially true for vehicles, where the rooftop panels can be difficult to access from the ground or where the vehicle roof may not be walkable (Airstreams etc.).
2. The second thing to remember is to always use distilled water to clean solar panels. Hard water can leave mineral deposits, and soft water can cause microcracking if there is a high temperature differential between water and panel. Use a soft cloth, nothing abrasive at all. It’s very important to avoid scratching the surface of the panel.
3. Always clean panels in the morning, before they heat up. This prevents microcracking and/or frame warping from soft and/or cold water.
4. Don’t use any detergents or cleaners unless absolutely necessary (see below). In almost all cases, plain distilled water and a little elbow grease will take care of things. The reason for avoiding cleaning agents or harsh chemicals when possible is that most panels are not just tempered glass, the glass also has a special anti-reflective coating that can be damaged if using inappropriate cleaning agents (bleach, vinegar, etc.). They can also attract particles to the panel surface (see below).
5. For a last resort, in extreme cases (tree sap/pitch, bird droppings), Windex outdoor glass and patio cleaner can be used. It will not void any panel warranties that we’re aware of. Before doing this, use a hard plastic scraping device with a smooth edge (e.g. a windshield ice scraper) and scrape off as much as possible. We have even used razor blades sometimes. Then carefully clean the remaining areas with a soft brush or non-abrasive cloth. Take care to avoid getting the cleaner on the edge of the panel frame where it meets the metal, this is where the seal is. You may want to use a Q-tip for dirty areas close to the frame edge. Only use the cleaner where it is needed on the dirty panels.
6. For anyone who wants to pursue deep cleaning, professional solar panel cleaners is available in some areas (this being said, we do not have any specific references or recommendations). This type of cleaning uses a waterfed pole with a filtration system that produces ultra pure water (filters should be at a minimum of de-ionized water filtration and reverse osmosis (commonly referred to as DI/RO water). No cleaning agents are used. No chemicals means cleaning panels for longer, as cleaning agents leave a coating that actually attracts particles. The brush head must be soft or medium bristles which are typical of almost all waterfed poles, but be sure to double check with the solar cleaning company.
7. The last thing to remember is that shade is always more of an issue for panel production than dirt or dust. Only clean when needed with minimal maintenance, or let nature do the work when it rains. Professional help when it comes to solar cleaning is almost always used for two specific user types: homeowners with front-facing residential panels who want or need them to look their best, and large utility-scale solar farms where every percentage point of production matters. For the vast majority of RV users, regular maintenance and cleaning will be an infrequent chore at worst.
** For additional reading on the research supporting the superior results of using distilled water for cleaning, we recommend Alisson Luis Boeing’s work here:
https://digitalscholarship.unlv.edu/thesesdissertations/3219/
