Rain!

[cwagz]

Seems like the cleaning my panels got last night from the rain might be worth about 700 to 900 watts on todays peak.

Anyone else have a similar experience? This was probably the first good cleaning they have had this season.

[jasonacox]

Hi Chad, yes, we see 10-20% improvement in kWh/day after cleaning. I do see a bump on peak too.

When the Tesla installers were here, I asked them about cleaning. They suggested every 6-12 months and to use "only water". A few months after the install, I noticed that the fires in our area had left a layer of ash on the panels. I decided to clean them myself. I set up the ladder on our 2 story house and hauled the water hose up to the root. My wife helped. She sat in the back yard in a lawn chair with her phone, "ready to call the ambulance." I admit, there were a few heart stopping moments as I juggled the hose, mop and squeegee. I lost my footing on the wet roof. Thankfully, I caught myself before I went over the edge. My wife was already dialing 911. I got back up and managed to finish the "job" but vowed to explore solar panel cleaning companies if I survived this adventure.

We had a "mud rain" not too long ago that just left everything covered in dust. It looked pretty terrible. I had found a company that would clean our panels for $120. Reflecting back on my DIY cleaning adventure, I gladly opened up my wallet. They did a phenomenal job and even sent before/after pictures. This will show the level of the "dirty" which wasn't terrible, but the end result was beautiful:

The cleaning did have a positive impact in our daily kWh daily production, from 43kWh to 48kWh (~12% increase).

I didn't expect to see a lot. I haven't done a lot of research, but a quick scan of studies shows that dirty panels can drop production 5-25%. I did find this from UC San Diego:

"Researchers found panels that hadn't been cleaned, or rained on, for 145 days during a summer drought in California, lost only 7.4 percent of their efficiency."

I think the positive part of that is that even dirty panels are doing an amazing job at generation. But, I must confess, my motivation for cleaning is somewhat more vanity driven. I love the hi-tech look of the clean panels. I think we probably wash our cars for the same reason (less about efficiency) but I will also keep hoping and praying for rain to do the work for me. Otherwise, I have a good company to do the cleaning, because I won't be juggling that stuff up on the roof again. 😄

[cwagz]

This is great information. Glad you didn't go over the edge! I guess I shouldn't be surprised by the gain from a cleaning. I was just hoping to never have to actually think about cleaning the panels. After seeing the improvement, it will be hard to ignore though. My highest producing day was 6/18/22 with 78kWh. Right after the early AM rain on 8/5/22 I am making 70kWh again. It looks like I probably could have produced a lot more all spring / summer if I would have cleaned the panels after the Santa Ana winds blew dirt all over everything earlier this year.

No way I would attempt to clean mine up on my roof. I probably would have gone over the edge.

I am going to start looking for a company to do the cleaning just in case our next rain is too far away.

[jasonacox]

Nice! Great graph. As to the wish to have done this earlier, I had the same thought. I know they were dirty during the highest peak solar days. We maxed out at 51 kWh/day but wonder where it could have been if they were clean.

I saw on google that the typical cost is $3-$10/panel. I can confirm that. I'm in Santa Clarita Valley and found Harold @ Clarity Solar Solutions and their rate is $6/panel. I asked him to also clean the Tesla skirt/frame. No extra charge but it sure makes it look nice. Worth asking if you have the skirts.