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!
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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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