Jan L. Green PC

Do Solar Panels Work When they Get Dirty?

Living in dusty Phoenix, I’ve heard rumors that dust has an effect on solar panel power production.   It stands to reason that a layer of dust might diminish the sun’s rays from being absorbed completely by the panels.   So the big question is, do solar panels work when they get dirty? 

Panels can collect more than just dust.  Birds might find a spot to perch above an array, adding a layer of “you know what.”  That layer of “you know what” can accumulate and reduce a panel’s production.   Between that and dust, efficiency can be impacted.  But how much of a reduction in power?    

Now that apps have been created that show the power generation for each panel at the push of a button, it can be easier to track.  Power production can be tracked for a daily or monthly average.  Comparing that average might show a difference in production over time if there isn’t any significant rainfall. 

Rain is scarce in Arizona.  On average, the Phoenix area receives about 7″ a year, which is why the city is aptly named “The Valley of the Sun.”    Without a lot of rainfall,  panels accumulate dirt!  

Of course this varies by location, so this information is specific to the Phoenix area.

If your panels produce on average 1.37Kwh per day like mine do, then it’s easy to follow.  Looking at my app on the same sunny day historically, it would be easy to calculate production after being installed for about 6 months with no significant rainfall.  Mine were installed in mid-August so I’ll need a couple more months to compare production. 

But how much of a reduction can you expect?  Some sites that I visited reflect a 5% reduction, depending on build-up, while others show a 2.3% reduction.   Also, some solar panels don’t have a drain at each panel allowing water build-up to occur, which can create a film at the bottom portion of a panel.  

Researching this topic online, I saw a very good article about cleaning panels.  The article, written by Greener Choices states that cleaning services , explains that the cost by a cleaning service is oftentimes higher than the energy savings.  

Another article shares that net result of dirty panels after a good rain.  This would be a good comparison because their numbers show a 1.85% net loss AFTER the rain in power production.  This is pretty insignificant in my opinion. 

Another factor to consider, solar panels have become even more efficient and the cost of panels has dropped dramatically during the last 5 years.  So the cost to produce power has dropped significantly. 

So the answer – it depends.  If your panels are very dirty, wash them.  But don’t use any chemicals, just mild soap and water.  If you receive rain periodically, that should be enough, but check for birds!  

This is another GREEN TIP in a series.  If you have questions, please contact me.  And if you’re looking to buy or sell a home in the Phoenix area, please make sure to use a reputable, knowledgeable agent!

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