How To Clean Solar Panels

How To Clean Solar Panels

How To Clean Solar Panels.

Dirty solar panels can reduce power-generating output by 20% or more by blocking sunshine from penetrating the glass and exciting the electrons underneath. Ash fallout from wildfires has been known to reduce power production by as much as 50% if not washed off.

One of our monitored solar energy sites is in Templeton, CA, on a dusty road. The dirty panels were producing 744 kWh. The solar panels were cleaned, allowed to heat back up, and re-tested. The clean system was then producing 910 kWh. The clean panels were producing 21% more electricity than the dirty panels were just an hour earlier. At 22¢ per kWh, the clean system produces $37 more energy per month than the dirty system, or $440 for the year. Results may vary depending on how dirty the panels are to begin with. Washing off slightly dusty panels is probably not worth the time and effort compared to the savings. See before and after panel below.

Note: Check with the solar panel manufacturer for specific recommendations for cleaning, and follow those recommendations.


  • A soft brush, and extension pole. I like the one found at Camping World for $15.49. It has a soft scrubber made for glass on one side, and a squeegee on the other. The pole expands from 48” to 84”.
  • A hose long enough to reach your panels
  • A non-abrasive, mild soap, such as Dawn dishwashing liquid.
  • A bucket

squeegee for cleaning solar panels


Plan on cleaning your system when it is cool outside, either early in the morning, or early evening. The glass will not like cold water being sprayed on it when the temperature is 100° outside.


  1. Fill your bucket with clean water and soap.
  2. Rinse off your array with the hose to remove all loose dirt.
  3. Dip your scrub brush in the soapy bucket and scrub the entire surface of the panels until clean. Be careful not to touch the sides or underside. Also, avoid contact with any wiring harnesses and/or cables.
  4. Rinse off with hose.
  5. Squeegee dry.
  6. Go on to the next two to three panels until all are clean.

If cleaning your solar panels requires you to climb on your roof, be extra cautious. Set your ladder securely and be mindful of a slippery surface when the roof is wet.

A dirty solar panel can reduce output by up to 30% or more.

For those who do not wish to clean their panels, or are unable to do so safely, Solarponics can clean them for you. Panel cleaning service starts at $174.95. Call us for an exact cost for a cleaning.

A lot of customers ask if the rain is enough to clean their panels. Yes and no. Rain will rinse off your panels, but similar to spraying your car with a garden hose. The hose will wash off the loose dust. But the car still has a layer of dirt on it. Google conducted research on panel efficiency when dirty, and concluded that solar panels that were cleaned professionally had a 12% higher output compared to those cleaned by the rain.

We recommend cleaning your panels annually, in the springtime. Be sure to monitor your output regularly and look for drops in output over time. This is an indication of heavily soiled panels.

© 2017 Solarponics, Inc.



Wildfires and Solar Panels

Wildfires and Solar Panels

ATASCADERO, CA August 24, 2016 – Sitting around the table in the Solarponics office at our usual Monday morning status meeting, we were chatting about the wildfires and how hazy it was outside. That led us to wonder how much that haze could be affecting solar panel power production.

But what about smoke? Does smoke in the atmosphere decrease solar panel productivity, or reflect more light similar to fog?

Wild fires release greenhouse gasses sending soot and other aerosol particles such as carbon into the atmosphere. These particles do not reflect light, they absorb light, reducing the intensity of sunlight and thus reducing the power generation of a solar panel.

In hazy conditions from wildfire smoke, which we are experiencing in Paso Robles, one of our monitored solar energy sites is producing 685.708kWh/day. The week prior, clear and sunny conditions, that same system was producing an average of 838.168/day. That’s a 19% net loss of energy production. The average home solar system size is 7kW in size, equating to a $1.60 kWh net loss/day under the same conditions.

In wildfire areas that experience heavy ash, the ash itself will settle on solar panels blocking sunlight, much like a heavy buildup of dust would do. The heavy ash sediment has been known to reduce power production by as much as 40% or more if not washed off.

Heavily soiled panels of Solarponics monitored system.

Heavily soiled solar panels.

The manufacturers of solar panels state that anything that reduces or blocks the sunlight from reaching the panel surface will reduce energy production.

Interestingly, there is something called the Edge of Cloud Effect. In partially cloudy conditions, it is possible and probable that your solar system will over produce. As the sun peaks through the clouds and hits your panels with direct sunlight, there is a great amount of reflected light from the clouds that bombards your panels. The direct light combines with reflected light to cause your panels to produce more power than just the sun alone would on a clear day.

According to the National Renewable Energy Laboratory, light fog conditions can also slightly increase power production greater than a clear sunny day alone, similar to the Edge of Cloud Effect.

Firefighters and solar panel safety.