You got your rooftop solar array, you’re stoked with your zeroed-out electric bill, and you’ve plugged in your EV to drive on sunshine. Then one month, you notice your electric bill gets a little bit greater than zero. Then the next month, same thing. You do what most normal people would do — blame your kids — and that makes you feel better for a little while, but then the kids, who are part of the Sunrise Movement and are really concerned about climate change, stop playing XBox every night for a whole month and instead read books like the model kids they are, and your bill still comes in greater than zero. Is it possible your solar panels aren’t at the top of their game?
Solar panels these days should last 25-30 years with good performance. So if yours are not long in the tooth, it’s definitely possible there’s something not working. If you’re not monitoring your solar system, it’s possible that one of the panels, one of the strings, or any number of things might be malfunctioning. Monitoring software (like Enphase) should be able to tell you which panel, string, or inverter is not working right, and odds are, you have a warranty with your solar system that will allow you to call your installer and get them to come set it right.
It’s also possible that your panels need some cleaning. “Cleaning?” I hear you say, “They get rained on all the time and it’s not like anyone is spilling food on them — what cleaning would they possibly need?”
As it turns out, the rain might be part of the problem. With many solar panels, seams and edges can hold just a little bit of water. if they do, plants, mold, and mildew can start to grow in those seams/edges. By itself, that wouldn’t amount to much interruption of photons from the sun creating electricity for your home. However, as nature does, that little bit of material then acts like a sponge and holds a little more water and the stuff moves up the panel. I’ve seen panels so covered that light could surely not penetrate.
Also, bird sh*t. It happens.
In the case of solar panels covered in doo or moss, simply cleaning with water and a very soft brush should do the trick. The trick, so to speak, though, is safety. For instance, the dude in the pic above is totally not OSHA safe — I mean, standing, not strapped in, on a slippery glass panel while applying liquid cleaner? Solid work, my friend. People, don’t do that. Also, make sure you contact your installer, check your warranty, etc., to make sure anything you or a company you hire do it right so that it doesn’t void your warranty. There’s really no reason to use anything but water and a little elbow grease (emphasis on “little”…you definitely don’t want to scrub or scratch the panels). It’s literally just the physical barrier created by debris, moss, etc., that needs to be cleaned away to allow the sun to shine on in.
There are companies that do solar panel cleaning, and many of them will also check for rust, corrosion, wires that have come loose, and more, and fix them up for you. They’ll spray some rust treatment, spot check connections, and let you know what they find that needs to be escalated. A simple Google or Yelp search in your area will do the trick, usually. If there isn’t one in your area, ask your PV installer what they recommend.
When and how often?
The question of when to do this and how often is going to be, like a lot of other questions about home efficiency, largely personal to the situation. In areas where there’s a lot of rain and clouds, the mossy growth is a bigger problem, as small puddles of water don’t evaporate well. In areas with large amounts of pollen and dry weather, then it’s likely best to clean the panels during pollen season, or right after. In areas with dry weather and lots of dust, a thorough cleaning once a year will help keep more photons going through, and may pencil well. Bird migrations? Maybe just wait til they’ve moved onward in their migratory journey and then take a look and see how much fertilizer they’ve so generously given.
Get to know your local climate and patterns, and you can probably just think through the best option.
Photo of dude cleaning panels in full hazmat gear courtesy of Pixabay. Not sure why he’s wearing all that, since it’s typically just water and a soft brush that is used to clean solar panels. But hey, you get what you pay for when you get free images to use on the web. Also, the OSHA stuff is real. That is really, really unsafe what he’s doing there.