Solar panel maintenance – fact or fiction?

Catchy title, right?

Why on earth would I even suggest that your solar panels don’t require maintenance – or do they? Well…the answer to that question is quite complex – but only if you subscribe to the particle theory of light (wait – didn’t they decide that light was both a wave AND a particle?)

GET TO THE POINT MAN!!

Ok… so we get this question a lot: Josh, do I need to have your team come to my home (or business) to inspect and/or clean my solar panels regularly?

The answer: MAYBE

Long ago (in PV solar world terms), solar panel manufacturers used to send us a piece of paper taped to each solar panel. Once you found the correct language you could read, you were introduced to your new solar panels (and their warranty, operation, and “maintenance” requirements).

If you had the gumption to wade through the overly-technical description of the product, you landed at a section called “maintenance and cleaning”…and this is what all solar panel manufacturers would tell you:

“If you have installed your solar panels with at least a 10° tilt (most home roofs are at least 18° or more) AND your region gets at least 12” of rainfall annually, then there is no need to manually clean your solar panels”

I always felt like this was a great introduction into the “what-if’s” part of the discussion:

1) What if I live on a dusty road and the solar panels get that dust?

2) What if I live next to a field that a farmer cultivates each year, and it throws up a lot of dust?

3) What if I come out during the late spring and I see my car is covered with (ugh) pollen?

4) What if…

This is where the answer isn’t quite so cut and dry as the manufacturers would have you believe – because if you meet their installation suggestions, then technically you wouldn’t need to clean your panels, right?

Well…technically…yes. That is true. And yes, we have customers who do not ever do more than Mother Nature offers to do for free. And this is also where the discussion veers into physics (specifically the physics of light and the science behind solar cells).

Fact: Solar panels/cells LOVE the blue and yellow spectrums of light

Fact: Solar panels/cells don’t really notice red spectrums of light (including ultra-violet and infrared).

What does the color spectrum have to do with cleaning my solar panels, you ask?

Well, it matters a lot.

It turns out that the human eye loves the red spectrum of light (without red, we wouldn’t notice if the car was dirty with dust). Without red, we might not appreciate the subtle differences in several shades of browns, grays, etc.

So ask yourself: what color is the dust on your solar panels? Is it brown(ish)? Gray(ish)? Or is it yellow pollen? And if it’s brown(ish) or gray(ish), I shouldn’t need to clean my panels manually, right?

To prove this to myself, I showed up early for Sunday dinner at my parents home several years ago. It was a wonderfully sunny day. Their solar panels should have been blasting out power (and they were).

But…

They were SO dirty that when I drove up to the home, I couldn’t see the individual cells that make up the solar panel itself – the panels were THAT dirty.

So…I broke out the hose and decided to rinse them from the ground.

Before I rinsed them off, the system said it was producing 7,700(ish) watts of power.

After I rinsed them off (and they dried almost immediately from the heat), the system was producing SLIGHTLY more power (7,800-ish watts of power).

And this led me to assess their production report we produced before installing the solar panels (more on that later – but a production report tells us if your home is a good candidate for solar).

What I found was that the report estimated roughly a 2% loss in power output per year from “soiling” – and unsurprisingly the math worked out as expected – their system was seeing a small (less than 2%) reduction in power production when the panels were so dirty I couldn’t even see the cells.

So…what gives, right?

Remember when I said that solar panels love blue and yellow light, but don’t really care about red light? Well, my human eyes saw a “dirty” solar panel because the dirt I was seeing was brown(ish) in color – so to me, they were dirty.

But…

The solar panels “eyes” (ie: the cells) didn’t seem to notice the same “dirt” that I was seeing. And in that “eureka” moment, I realized that the manufacturers, the science, the reports, and estimates, and real-world trials were lining up with the very simple statement of:

“If you have installed your solar panels with at least a 10° tilt (most home roofs are at least 18° or more) AND your region gets at least 12” of rainfall annually, then there is no need to manually clean your solar panels”

So…DO you need to clean your solar panels?

Sometimes, yes.

If you happen to live near a lot of fir trees that produce a lot of pollen (and you notice a yellow sheen of pollen on your solar panels) – then break out the hose and give them a rinse. Nothing special – and ideally you won’t need to do much more than MAYBE get a little higher off the ground (say…on a ladder) so you can get the water onto the solar panels.

What if your neighbor tills up his field and it throws a ton of dust onto your solar panels – should you have them cleaned? In my opinion – break out the hose and clean what you can. You WILL notice a power output increase, but in terms of 12-month production, it’s unlikely to move the needle much.

What if wild-fires blow and throw a lot of ash onto my solar panels? Should I clean them? In my opinion – yes! But carefully. Anyone who was alive for the Mount St. Helens eruption remembers all of the warnings on the news and in the papers about smearing dust on your beautifully painted car – it would scratch the bejezus out of it! So…carefully my friends! Water only until you get the bulk of the ash off of the panels. Then – if you decide – you can carefully get a squeegee and WATER to complete the cleaning.

What about our commercial customers whose panels are less than 18° in tilt? Should they consider cleaning their panels regularly? In my opinion – yes. The slight tilt of the solar panels is not enough to rid the panel of build-up at the bottom edges of the solar panel. We recommend water and/or a squeegee 2x per year (late spring and mid-summer). Cleaning the low-tilt solar panels during these times is usually adequate to keep them producing the expected amount of power per year.

So… what about those companies selling fancy “solar panel cleaning kits”?

In a single word: DON’T.

Don’t buy it, stop reading about it, and don’t let them scare you into the purchase.

Solar panels are constructed VERY similar to the windshield of your car. And as such – you should use the same care when cleaning them (as you would your windshield):

· NO harsh chemicals

· NO hard/stiff brushes

· NO scraping with anything more than a rubber squeegee.

So…if my solar panels need a “little bit of help” getting clean, are there any products I CAN use?

Well my friends – the easiest answer I can give you is this:

Biodegradable Dish Soap.

Yup. Good old-fashioned Dawn Dish Soap.

There’s your “exotic” cleaning agent. If you can clean up wildlife (after an oil-spill) with this stuff – and it’s safe to use on them – then it’s also gentle enough for your solar panels (and the gaskets that surround them (between the metal frame and the glass) but also can offer the extra “help” your panels may need to break down excessive dirt and grime.

So… there you have it: most homes and businesses will not need to clean their panels. But if you do, hopefully I’ve given you enough information here to do it simply and without the need to call a company to do it for you!


Thanks for reading

Josh

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