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  • Heather Zimmer

To Clean or Not to Clean: Should I Clean My Solar Panels?

At Sunpath, we are committed to helping you get the most out of your solar investment,

and we often get asked by our customers if they should clean their solar panels on an

annual or semi-annual basis. The answer is… it really just depends!


Why Clean Your Solar Panels?

Clean solar panels will let more light through the glass to the energy-producing cells

underneath, which in turn will maximize their efficiency and power production. Dirt,

pollen, leaves and other debris can block light transmission which can impact power

production by a few percent if left unchecked.


Why Not Clean Your Solar Panels?

It is true that solar panels covered in dust or pollen will produce less power, but in most

cases your installation company has already factored in “soiling” to the long-term energy

production estimate for your system. And…lucky us, living in Oregon means that for 8 –

9 months of the year mother nature’s rainfall will typically do the job for you!


If your roof is easy to access, or you can use a jet nozzle on a hose to wash the panels,

cleaning them yourself is an option to consider. However, if you have a two or three-

story roof, a steep pitched roof, or any other condition that makes solar panel cleaning a

safety concern, we recommend leaving panel cleaning to a professional roofing

company or panel cleaning service. The added caveat being, in most cases the cost

you will pay for your solar panels to be cleaned will never be recovered in additional

power generation (most panel cleaning will only result in a 1% - 3% bump in power

production).


What About Moss Buildup?

We do recommend having moss killer or some other moss abatement steps taken for

your roof (whether you have solar panels, or not). Over time moss can buildup under

solar arrays, particularly in the more shaded areas, and on east and west-facing roof

slopes where it stays a bit cooler. Substantial moss buildup can provide a pathway for

water to get under the roofing shingle as the moss gets under the shingle and can lift

them up over time. The safest way to kill moss under a solar array is to spread moss

killing granules on the ridge of the roof, or the area directly above the array, and let the

rain take care of washing it down underneath the solar panels to kill the moss. The

same guidance applies – if you are unable to safely access your roof, leave this to a

professional cleaning service.


If You Decide to Clean Your Solar Panels (and it’s safe to do so): A Step-

by-Step Guide


Materials Needed:

  • Soft brush or squeegee with a long extension handle

  • Mild soap (optional)

  • Bucket

  • Hose with a spray nozzle


Steps:

1. Prioritize Safety:

Timing: Clean your panels in the early morning or late evening when they’re cool

to the touch to avoid burns, as well as damage from thermal shock to the

panels.

Power Down: Ensure your solar panel system is turned off to prevent electrical

hazards.

Safety Gear: If your panels are roof-mounted, use proper safety gear to prevent

falls.

2. “Dry Cleaning” Without Water is Not Recommended!

3. Wet Cleaning: Prepare Cleaning Solution: Fill a bucket with clean water (distilled water is ideal to prevent mineral deposits, but not necessary). Add a small amount of mild soap.

Rinse Panels: Use a hose with a spray nozzle to rinse off the panels. Avoid

using high-pressure water (no pressure washers!) to prevent damage.

Wipe Panels: Dip a squeegee or long-handled brush (with soft bristles) in the

soapy water and gently wipe the panels to remove any stubborn dirt or grime.

Final Rinse: Rinse the panels again with clean water to remove any soap

residue.

Cleaning Frequency: Once or twice a year, typically during summer months

when rain is infrequent, or more frequently if you live in a particularly dusty

area or near pollution sources.

Optimal Conditions: Choose a cool, overcast day for cleaning to prevent water

from evaporating too quickly, which can leave spots or soap residue.

Avoid Harsh Materials: Never use abrasive materials or harsh chemicals, as

these can scratch or damage the glass on the panels (preventing light

transmission to the solar cells underneath).


By following this guide, you can determine if it is safe to clean your own solar panels, or

if hiring a professional is needed. If you have any questions about how to clean your

panels, reach out! We’re here to help!

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Welcome to Illuminate, your comprehensive guide to solar installation! Whether you're a seasoned environmental enthusiast or just dipping your toes into the world of renewable energy, this blog is designed to illuminate the path to harnessing the power of the sun.

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