Clean your solar panels!

[nwdiver]

Meh... totally depends. If cleaning the panels once resulted in a 10% improvement for the next ~3 months it might be worth it. From what I've seen the boost only lasts ~2 weeks. It's not worth cleaning the panels 25 times a year for $20 of increased output. And a good storm does just as good a job as I can. I always feel like a sucker if I spend an hour cleaning the panels then we get a good downpour 2 days later...

Just add ~10% more panels and call it automatic cleaning

 

[nvx1977]

Most companies will discourage cleaning, mostly for safety reasons.

I'm in New England and have a large (18kW) array on a steep (45 degree) roof. Never had to clean. Rain does the job during the warm season. Snow sliding off does the job in the winter.

 

[ToddRLockwood]

Your post pretty much convinced me not to get solar panels. The part of the roof I'd have to put them is 3 stories up with a pretty good pitch. No way I'd be able to get up there and clean them without some special equipment...

Another great option in some states is to lease or purchase panels in a community solar project that connects to the same utility that you use. This earns you kWh credits against your home utility account. Works beautifully here in Vermont.

 

[BobbyGood]

My solar installer advised me not to clean my solar panels - just let the rain do it. And mostly I've done that. They were installed June/July of 2014 and the first couple of years I got up there with a mop and a hose and cleaned them, but its a 2-hour pain in the a@@ and I've been lazy.

Well, today I finally got up there and cleaned them again, and based on my Enphase system and my Neurio, I'm now getting 10-12% more power.

The sun has been mostly shining yesterday and today. There are some clouds, but when they clear the panels go to max power. Yesterday that was 4.9kw. Today, so far (its right at noon as I type) I am getting max peaks of 5.4kw.

Moral of this story, clean your solar panels!

See picture - I took this just now to show you my panels and guess what! I missed one DAMMIT. (clearly visible in the picture) Now I have to crawl back up there... But it gives you an excellent "before" and "after" what the panels look like.

View attachment 412543


Below shows the first panel I cleaned. I sat the mop on the panel next to it, which killed that panels production. So you can compare the output of the topmost panel after cleaning, with the bottom panels. Clear improvement.

View attachment 412558

You should clean your panels whenever they get a buildup of pollen and dirt. It makes a big difference just like it does with glasses. By the way your Enphase diagram is showing that panel #2 from the top is suboptimal. This is normally the case when the microinverter goes bad. in rare instances it is the panel diodes. Correcting the bad microinverter and cleaning the dirty panels will put you back at optimal output. I clean my panels twice a year. In Florida we have roofs without a lot of slope so cleaning makes a difference.

 

[TORQU3]

Another great option in some states is to lease or purchase panels in a community solar project that connects to the same utility that you use. This earns you kWh credits against your home utility account. Works beautifully here in Vermont.

This is what I do as well. I got a very good rate, not all projects have rates better than the utility. Although I got a good rate, I'm sure it's still probably not as good as buying your own panels. It is a lot easier though. I just had to wait a while for the project to come online. It does save me quite a bit of money. For example, I pay $X a month during the shortest days in the winter my electric bill is credited about the same amount I pay to the community shared solar project. During the the remainder of the year, the credit on my utility bill is 2x-3x what I pay to the community shared solar project. Once I go over what I was credited, I'm buying at market rates. I try to charge my car at work as much as possible to avoid going over.

 

[Gray468]

Solar panels in Santa Barbara for almost 6 years. Drought and fires motivated me to clean them periodically. Bought a massive squeegee pole and fret that I will drop it end wise on the glass... but a quick sponge and flip to squeegee does the trick. 24 panels in about 30 mins. An hour full up. Most of the time, measure about a 3% improvement.

I agree with an earlier post, that 3% improvement does not last long. Dust is back in a few weeks. But I feel better for having tried.

Cloud cover and temp are way bigger factors. They even swamp degradation. But the real measure is against consumption. Year five was my best so far in terms of net production. Swapping an electric dryer for gas had a much bigger impact than any cleaning of panel’s would get. That combined with probably the sunniest year of the 5 produced over a MW more than consumed. Yes, that includes charging my S100D.

This year production is way down due to inordinate cloud cover. But daily production on sunny days are way up, best ever, because it’s 10 degrees F or more cooler than usual for this time of year. Not really able to measure degradation over 5.5 years as weather swamps the effect.

So ya, here, especially this year thankfully a wet one, cleaning not needed. But after a month of dry with no rain in sight... up I go up to earn my 3%.... about 1 kWh for a day... 17 cents on tier 1. But really 3 cents since I over produce and that’s what I earn from SCE. Bite me.

 

[Togg]

It also might depend on the mineral quantity in your water.

Rain water is free of minerals, and thus won't build up a film of them, but for many people who have hard water cleaning regularly might not be a good idea. With multiple cleanings you may never get the minerals off and thus pertinently damage your panels.

 

[compo11]

You should clean your panels whenever they get a buildup of pollen and dirt. It makes a big difference just like it does with glasses. By the way your Enphase diagram is showing that panel #2 from the top is suboptimal. This is normally the case when the microinverter goes bad. in rare instances it is the panel diodes. Correcting the bad microinverter and cleaning the dirty panels will put you back at optimal output. I clean my panels twice a year. In Florida we have roofs without a lot of slope so cleaning makes a difference.

Hey Bobbygood,I also live in the Orlando area and my roof has a slope,I would think those torrential downpours we get here in Orlando would be enough to keep them clean......How much does it cost to have them cleaned???Will you recover the cost of cleaning ,if not I probably won't do it...thinking of installing some this year.....any insights with a local slant???

 

[BcHoward]

I pay a local solar panel cleaning company to come inspect and clean my panels every 3 months. The price is very reasonable and well worth it for what is maybe my biggest investment other than my house and Tesla. Plus I'm a senior and there's no way I'm climbing up on my roof.

 

[yousexy]

my house is 3 story high, I can't do it myself. hiring someone might cost more than the benefit.

 

[Timothy]

I have my panels on a hillside rack--not on the roof. Our system was installed in 2008 (and the amount we have saved on electricity bills has paid for the system!) I have cleaned the panels at least a dozen times--and can measure no difference in electricity production. Our rainy season (Oct-May) seems to clean them adequately. When I see grime on the panels in the summer, I usually clean them (about once a year at this point) just because--but it has not made a measurable difference in electricity production.

 

[Videographer]

I have my panels on a shallow-pitch roof on a single-story building, and yes, I do wash them from time to time. In fact, I even shovel (or garage-broom) snow off of them in the winter. Yeah, I'm nuts.

One more "pollutant" to keep an eye on in the spring is pollen. I've had the panels covered in very opaque yellow dust every spring for years now. Long ago I bought a professional window-washing squeegee/rag combo on a long aluminum pole, it's good enough for my situation.

 

[Silicon Desert]

The question that has to be asked is the cost of cleaning the solar panels worth the extra energy you get from cleaning them?
For me it is a No. I had my panels cleaned once and it just isn't worth the cost. I have a two-story house and no way am I climbing up on my roof to clean my panels. To many ways that could go wrong.

Precisely my thought and my policy. Not worth the extra small power (from past years of experience on 3 homes), and the risk of personal injury.

As I think we all know, there are a lot of variables at play. The main one being what kind of an area are people located. My San Francisco East bay home was getting more dirt than the one up here in Nevada where there is very little dirt and then the rain and snow do a good job of keeping them clean enough. I've also noticed in recent years that often just spraying them down does about as much improvement as wiping them off. That is on my San Diego home just one story high and I can do it from the ground. Thus having about the same effect as a heavy rain.

As a side note for the OP, you probably know this, but you really can't accurately compare one day to the next day even if it is the very next day. What I am referring to here is you don't mention the cloud coverage comparison during the two days. I have noticed in the past that "Cloud enhancement" can account for as much as a 10-13% boost in power during parts of the day, so you can't look at just the peak power. However, having said that, yes, I'm sure you will see a boost in power to a small degree. Lastly, I wonder if the installer said "not to clean them", or "no need to clean them". I'd guess the later.

 

[Merrill]

I have experimented with cleaning vs not cleaning and I notice a difference when they are clean, I use a DI system with the fiberglass pole and brush. This works really well and easy to do, probably clean them 4 times a year depending on how dirty they are.

 

[mspohr]

I think it depends a lot on your environment. If you get a lot of dust/pollen and if they can be easily cleaned, it might be good to clean them. However, I've found that rain and snow do a good job by themselves.
In California, we don't have much rain during the summer and the panels can get dirty. In the spring, especially, we get a lot of tree pollen. I spray the accessible panels with a hose and this gives a bit of improvement but I have some which are not easily accessible and I leave these to the weather.
I only bother with cleaning since it's easy (cheap).
(Incidentally, I've noticed that I get a big jump in power output after I spray the panels but this lasts less than an hour. The cooling from the water improves output.)

 

[wyldtek]

Not only do we lack rain in CA in the summer but ash from any forest fires also settles on the panels. When we got our first heavy rainstorm earlier this year, I could smell the ash that was being rinsed off the roof and panels from the fires at the end of last year.

 

[Bob M]

The return on solar for me was huge. (Panel cleaning discussion at the end) They paid for themselves in 44 months. My electric bill 3 1/2 years ago was avg $270 per mo and gasoline $250. With a used Volt, I now pay less than $50 for gas, and $9.50 for electricity, even though I only generate 80% of what I use. Time of use pricing makes it slightly positive for the year. My net cost was $21k. Electricity and gas are both higher now and installed cost per watt for solar is about 30% cheaper and panel efficiencies are available over 20%. I would spend the extra for 21 1/2% panels and buy enough to cover future electric car purchases and a heat pumps (eliminate natural gas) for home and water heating. Batteries can be added later but buy the controller and micro inverters (Enphase is just coming out with these) which can integrate later battery purchases and also that can operate your whole system when the entire grid goes down. I believe for very little extra expense. As long as I have net metering and batteries are still so expensive, I will let PG&E be my almost free battery.
After my first full year, I sprayed and mopped clean my panels to see if it made any difference. They looked just a bit dusty. I could not detect any improvement at all. I got Solar World SW 285 panels (29 of them). My installer told me they had a special self cleaning coating so that rain or heavy dew would keep them clean. Last year they looked particularly dusty. I got on an A ladder and used a hose from the ground,( nice and safe) to make good rain on my 2 story house. That did the job. I could see maybe 10% improvement.

 

[Bob M]

I think it depends a lot on your environment. If you get a lot of dust/pollen and if they can be easily cleaned, it might be good to clean them. However, I've found that rain and snow do a good job by themselves.
In California, we don't have much rain during the summer and the panels can get dirty. In the spring, especially, we get a lot of tree pollen. I spray the accessible panels with a hose and this gives a bit of improvement but I have some which are not easily accessible and I leave these to the weather.
I only bother with cleaning since it's easy (cheap).
(Incidentally, I've noticed that I get a big jump in power output after I spray the panels but this lasts less than an hour. The cooling from the water improves output.)

They advise to not spray the in the sun or you risk panel damage.

 

[La Piazza]

I wonder... Has anyone tried the "no-Rinse" car wash liquid? The "No Rinse" solution says it is suppose to break down dirt. I consistently use it to clean my car. First with a solution using a bug sprayer -which of course would be fairly easy to spray on the panels.

 

[SSonnentag]

That's a lot of solar, plus the batteries! How long have you had the solar panels? Installed same time as batteries? If you've never cleaned them, is your peak power still as high as its always been?

What level do you keep the batteries? How often do they drain completely? Do they charge to full every day? every week? every month? How much power do you store and then use from the batteries daily, on average? You can tell I'm very curious how the batteries work.

We've had solar a bit over 10 years. The output this year is right on par with the first year. There are ups and downs in production due to weather conditions, but any degradation of the panels or inverters is minimal and cannot be seen in the average output. Our battery system was only installed this year. It is for backup purposes only as we are on a flat rate plan. They stay at 99% charge. When configured as backup power only, there is no user-adjustment for the battery charge. It always tops off in the morning when the sun hits the panels and drains 1-2% overnight, whether due to inherent losses or by design I do not know. I have not yet noticed any maintenance loading/discharging of the batteries.