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Cleaning solar panels and solar tiles

jboy210

Supporting Member
Supporting Member
Dec 2, 2016
5,509
3,495
Northern California
Hi,

How often does one need to clean solar panels and solar tiles here in California?

I saw someone's video on YouTube and he got a 34% increase in production from dirty, even with a so-so job of cleaning.
 

brian954

Member
Jul 7, 2019
36
8
Miami
I saw his video as well and I would imagine on the west coast solar panels should be cleaned every 3-6 months to keep optimal performance. I cringe thinking about how much power he has been losing as he mentioned he didn’t clean them for 18 months.

Where I live it rains at least a few times per week, I figure every year or so and I should be fine.
 

charlesj

Active Member
Oct 22, 2019
1,267
294
Monterey, CA
I clean mine about twice a year. Certainly after the pine pollen finished falling.
I do not go the the extreme that "clean" link shows though. ;)
 

bkp_duke

Well-Known Member
May 15, 2016
5,596
19,749
San Diego, CA
I would say don't bother.

We've had horribly dry and dusty conditions for 2 years, and I did a little experiment 6 months ago and paid someone $100 to hop on our roof and clean the panels. The efficiency improvement I could discern on monitoring was approximately 8%, and in a month that had dropped down to 4% or less because the panels had gotten dirty again. Literally, I could not get enough improvement in efficiency to justify the cost.

I now just wait for it to rain in the fall in San Diego and it does a good enough job of cleaning them off.
 
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charlesj

Active Member
Oct 22, 2019
1,267
294
Monterey, CA
Yes, I understand that if you have to pay for a cleaning, then it would not pay for itself.
I am still able to get up on that 2nd story roof and mop it. My time is free.

I guess I could move the $$$ from my right pocket to the left. ;):D
 
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KSilver2000

Active Member
Dec 23, 2017
1,368
2,438
CA
Tl;dr conclusion: Unless you’re doing it yourself, it’s a waste of money.

Against my solar installer’s advice, I paid $95 to get mine cleaned at the 1-year anniversary of getting my panels installed. I compared the energy generated at the 2nd year to my first year, and the difference was less than 3%!!! Have not cleaned it since, and have seen any noticeable difference in the energy report. Some of the loss was probably due to the aging PV panels and not dust accumulation.

Or, there could have been a significant loss in efficiency in subsequent years but more sun after the first year offset some of the loss? I highly doubt that.

But, then again, I guess everyone’s roof/house/neighborhood is slightly different, and my results may be different from others. I have LG panels if that matters in any way.
 
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boaterva

Supporting Member
Supporting Member
Apr 2, 2016
7,575
3,817
Northern Virginia, USA
I would assume if you get heavy rain (as we get periodically here in Virginia) it’s probably not needed. We just had a downpour last week and I’m still getting 7 kW of a peak 10 kW even with 6 weeks to go before minimums at 12/22.

Love to have easy access to the roof to see if there is any real dirt there after about 15 months but as on most suburban homes in NoVa it’s 20-30 feet up. Eek.
 
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jjrandorin

Moderator, Model 3, Tesla Energy Forums
Nov 28, 2018
10,857
12,583
Riverside Co. CA
I have had solar since 2015 and just had my panels cleaned for the first time a couple of weeks ago. I live in Temecula CA which is sunny, and hotter (and colder) than san diego. on my 8.745kW system, I normally get around 25-27kW per day this time of year on a sunny day. I am getting 27-31 kW so about 3-5kW total per day more production. I dont have any trees overlooking my panels, so they were just dirty from dust / pollen.
 

arnolddeleon

Supporting Member
Supporting Member
Jul 21, 2012
917
993
SF Bay Area
Paying someone to clean panels generally doesn't make economic sense, it is basically a wash (or situations vary) However I pay someone to clean my panels on occasion. The person I hire actually knows something about solar panels. So I get a maintenance inspection as part of the cleaning. In once case he recognized failing panels from BP and was able to help with putting in a warranty claim.
 
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VanillaAir_UK

Well-Known Member
Jun 17, 2019
8,458
5,991
Surrey, UK
I'm in UK and clean what I can reach of mine (lower 2/3rds) every couple of years with a soft pad on a long pole. I also so a quick squirt with the hose if got the house out and if we had prolonged dry spells and dust and/or large bird poo - both reoccur fairly quickly. Rain seems to do as good a job.

Doesn't seem to make much of a difference and certainly not worth paying for or risking injury. Certainly had no measurable degradation from first season.
 
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charlesj

Active Member
Oct 22, 2019
1,267
294
Monterey, CA
...
I compared the energy generated at the 2nd year to my first year, and the difference was less than 3%!!! ...
I really don't think that is a realistic comparison of production differences, let alone due to cleaning. Solar production from year to year greatly depends on weather from year to year, then the panel degradation over time.
I made a yearly chart broken down by months. I am in my 8th year and all I can conclude is that weather changes drives production the greatest. If you have micro inverters as I do, not all panels will produce the same power throughout the day, even on a relatively clear sky.
I noticed on my chart that May was the best producing month for the first 3 years.Next was August. Then it was June, July, back to June and again this year. The yearly production is also all over the place.

The only realistic way to measure the effects of cleaning is that video that measures right away before and after. But even that video I am not sure if the person measure correctly by somehow keeping the voltage constant or something like that.

It is a good practice.
 

KSilver2000

Active Member
Dec 23, 2017
1,368
2,438
CA
I really don't think that is a realistic comparison of production differences, let alone due to cleaning. Solar production from year to year greatly depends on weather from year to year, then the panel degradation over time.
I made a yearly chart broken down by months. I am in my 8th year and all I can conclude is that weather changes drives production the greatest. If you have micro inverters as I do, not all panels will produce the same power throughout the day, even on a relatively clear sky.
I noticed on my chart that May was the best producing month for the first 3 years.Next was August. Then it was June, July, back to June and again this year. The yearly production is also all over the place.

The only realistic way to measure the effects of cleaning is that video that measures right away before and after. But even that video I am not sure if the person measure correctly by somehow keeping the voltage constant or something like that.

It is a good practice.

You're getting down to the nitty gritty details. Overall, my point was the couple % variation from year to year makes it worthless to pay someone to clean my panels. (Yes, I do have microinverters). My solar edge app shows month-by-month comparison over successive years, and I see barely any difference from having cleaned it the first and only time.
I agree, there's no exact comparison you can do unless you specifically clean only half side of every panel. But, then you have to decide whether you clean the top half or the bottom half, left, or right....
 

Ulmo

Active Member
Jan 19, 2016
4,329
4,905
Vienna Woods, Aptos, California
Hi,

How often does one need to clean solar panels and solar tiles here in California?

I saw someone's video on YouTube and he got a 34% increase in production from dirty, even with a so-so job of cleaning.
You have to factor in the cost of an accident from cleaning them. What that really means is learn how to clean them without having an accident, and don't overclean them. In the future, drones will do this. For now, I'd like to know best practice, since I have trouble with it. In my area I don't have dust but in the Central Valley they sure do. I have moss! (It's humid here.) I generally don't overclean them. When they look terrible, I'll make sure I have some sort of accident-free session of doing something to clean them. If I lived where it was dusty, I'd look for some way to blow or rinse the dust off.

I've heard that using chemical soaps might wash off the anti-fogging and anti-growth coatings. I would be interested in recoating systems because of that potential, but not if it's just a scam, so I'd want to see tests of how effective recoating systems are. I don't presently know of any recoating systems.
 
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charlesj

Active Member
Oct 22, 2019
1,267
294
Monterey, CA
Ksilver2000, yes we agree if you have to pay, it is not very cost effective.
Just a side not, my panels variance over 7.5 years is about 170kWh from lowest to best panel.
I think I added up all 17 panels and it came close to a mWh.
 

jjrandorin

Moderator, Model 3, Tesla Energy Forums
Nov 28, 2018
10,857
12,583
Riverside Co. CA
You have to factor in the cost of an accident from cleaning them. What that really means is learn how to clean them without having an accident, and don't overclean them. In the future, drones will do this. For now, I'd like to know best practice, since I have trouble with it. In my area I don't have dust but in the Central Valley they sure do. I have moss! (It's humid here.) I generally don't overclean them. When they look terrible, I'll make sure I have some sort of accident-free session of doing something to clean them. If I lived where it was dusty, I'd look for some way to blow or rinse the dust off.

I've heard that using chemical soaps might wash off the anti-fogging and anti-growth coatings. I would be interested in recoating systems because of that potential, but not if it's just a scam, so I'd want to see tests of how effective recoating systems are. I don't presently know of any recoating systems.

Shrug, I paid someone to clean mine on my 2 story house. I have 34 Panels, and a cement tile roof, and the company I paid to clean them took before and after pictures. They used deionized water and a horsehair brush on a long handle to do it. The specific company I used is a window cleaning / screen replacing company that branched out years ago to include solar panel cleaning.

I dont think I am going to do this every year, but it does not tend to rain a lot here so they get pretty dirty. They took pictures to show me. Here is a before and after of the same set of panels:
 

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Merrill

Merrill
Jan 23, 2013
4,034
1,525
Sonoma, California
I do the cleaning myself with an extendable fiberglass pole and brush fed with DI water, some of my panels are on the flat part of my roof and the others are reachable from the ground. Does a good job and only need to do it in the summer, no rain and lots of dust.
 

Odiemac

Member
Apr 19, 2016
112
197
Hayward
We don’t need to re-invent the wheel here, there is a ton of data from grid-scale solar operators on “panel soiling”. They clean a control panel and measure its variance to soiled panels.

The data shows that most locations only lose a few percent performance between rains, except in areas where farming or construction kicks up a ton of dust, in which cases the impact can be 10%.

https://www.nrel.gov/docs/fy17osti/69131.pdf

AC58B455-E7FE-4DFD-822D-2E2730C8B402.jpeg
 
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charlesj

Active Member
Oct 22, 2019
1,267
294
Monterey, CA
Shrug, I paid someone to clean mine on my 2 story house. I have 34 Panels, and a cement tile roof, and the company I paid to clean them took before and after pictures. They used deionized water and a horsehair brush on a long handle to do it. The specific company I used is a window cleaning / screen replacing company that branched out years ago to include solar panel cleaning.

I dont think I am going to do this every year, but it does not tend to rain a lot here so they get pretty dirty. They took pictures to show me. Here is a before and after of the same set of panels:
Wow, yes, a great and difficult job there. No real walking space at the gutter to clean the bottom row.
 

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