Cleaning Dirty Solar Panels

Dirty Solar Panels: To Wash or Not to Wash.

This is a great question on solar panel care and one that comes up often. The link here is an experiment done by a solar company in Austin, Texas on the effect of dirty panels on solar production. Their conclusion is that a dirty solar panel will produce about 3.5% less than a clean solar panel. That is a far lower number than often thrown around by solar companies and washing services, which claim up to a 20% savings.

Now, this conclusion might have to do with the fact that Austin, Texas sees quite a bit of rain which the article cites as being responsible for about a 1.85% increase in production during a typical rain cleaning. In general circumstances, PV modules do not need much in the way of cleaning, however, certain parts of the country don’t get as much rain as other regions, so cleaning is sometimes necessary. We in Southern California have a far dryer and dustier environment so it should not be surprising to discover that our losses would be greater than the 3.5%, and up to 10-15% in severe cases.

But, for the sake of argument let’s just use the 3.5% number. The annualized losses per panel, assuming we cleaned the panel every year would be 15-20 kWh or about $6-$8 worth of electricity. A cleaning at $5-$6 per panel would appear not to lead to much of savings. But using this worst-case scenario, you’re still better than breaking even. And for most of us in Southern California, the savings will likely be more and thus be worth the time and money invested.

Add to that the fact that having a periodic cleaning will not only prevent the panels from getting progressively worse but will definitely extend the life of the panel. It will also get rid of the dirt that will not come off with a simple rain, like bird droppings, bee pollen, leaves/pine needles, and the accumulated dirt and stains at the bottom of the panels where water pools.

It is therefore our advice that you get your panels cleaned at least once a year, in between our winter/spring rainy season, preferably in the August/September time frame. Nearly every window washing company offers a solar panel cleaning service. They have all the right equipment, water, brushes, etc. to do a great job at cleaning panels. Ask your favorite window washer what they charge for cleaning your panels or go online and ask around for a reputable cleaner. Most window washers will perform this service using the required deionized water only (no soap or detergents) and a soft-bristled brush. If you’re doing it yourself be sure to follow those same directions and remember to do it when the weather is cool (early in the morning) to prevent the panels from cracking during the heat.

It is also important to keep track of PV solar panel maintenance. Our Sungenia team recommends regular inspections (every six months) of the system to ensure that all fixtures are securely tightened and corrosion-free, wiring is securely connected, properly arranged, and free of corrosion, cables are free of damage, and that there are no loose wiring or cables visibly hanging down the array.

For more information and answers to common solar questions visit our blog on Solar PV Panel Care. If you notice anything that appears dangerous or outside of normal weathering, give us a call or message us today.