Solar panels are very resilient and generally do not need to be cleaned often. However, on occasion, special circumstances exist, such as dust storms, snow, or an abundance of fallen leaves. In fact, a study was conducted in California where researchers discovered that “panels that hadn’t been cleaned or rained on, for 145 days during a summer drought in California, lost only 7.4 percent of their efficiency. Overall, for a typical residential solar system of 5 kilowatts, washing panels halfway through the summer would translate into a mere $20 gain in electricity production until the summer drought ends—in about 2 ½ months” (Cleaning solar panels often not worth the cost, engineers find (phys.org)).
Based on the data collected in California, it seems that the cost of having someone clean your solar panels isn’t justified. Hiring a cleaner or purchasing solar panel cleaning solution would actually be an extra expense. So what’s the best solution? Researchers decided that if your solar panels are placed on a five-degree angle when installed, most debris that falls on your roof should fall right off of the panels without any effort on your part.
However, if you’re someone who likes everything tidy top-to-bottom and ship-shape, there is a method you can use. Before you start cleaning, turn off the DC switch, which is located in the combiner box. “This is essential to guarantee your safety and to make sure that the solar panels won’t get damaged by water inside the junction box, exposed wires, or broken seals while DC electricity is flowing through the system. New PV systems in the U.S., according to NEC 2017, are now required to have a rapid shutdown system that will instantly reduce the voltage of the PV array to zero from an easy-access location inside the house or business. This will guarantee security in any case for the homeowners and firefighters as well. Always remember to push that red button in the rapid shutdown box before going to clean your solar panels” (How to Clean Your Solar Panels – Tips & Full Guide (ecotality.com)).
Another tip for cleaning your solar panels safely is to only use distilled water and gentle dish soap with a soft sponge being careful not to scratch the glass on the panels. Using distilled water prevents hard-water mineral buildup, and gentle dish soap doesn’t have a chemical reaction with the glass, which keeps your panels looking like new. In addition to these precautions, you should always use a gentle stream of water. Why? “Using high pressure to clean…solar panels can force water to enter into the junction box or plugs that are not 100% sealed. As a general approach, it is recommended that when using a hose, the pressure stays below 40bar. It is also recommended that…water jet cleaning creates a sheet of water spray at the nozzle to reduce the pressure received by the glass” (How to Clean Your Solar Panels – Tips & Full Guide (ecotality.com)).
Whether you decide to clean or not to clean your solar panels, you can rest at night knowing that the experts believe that it really doesn’t need to be done often. Literally, unless there’s thick sediment on your panels, there is no need to worry about cleanings or to lose any sleep over it. Now you can check one more thing off of your to-do list.