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Solar panel system production down three months in a row

GAJ

GAJ

Well-known member
Joined
Mar 10, 2008
Location
SANTA ROSA
Moto(s)
F800ST
Name
Geoff
how about you all?

Maybe it is weather related?

I'm in Santa Rosa.

Sept, Oct and Nov production vs prior year all down individually, and 20 percent as a whole.

Mind you last September I did have the panels cleaned but they don't look all that dirty at the moment.

Just wondering if I'm the only one experiencing that the past three months.

Thanks.
 
Typical, annual production is a bell curve

Average annual looks like this in SF, South facing, no shade.

Assuming everything is working properly,
Panels only degrade less than 1% per year on average.
Local weather can impact year-over-year production, cloudy days, fog, rain vary every year.
Do you have a Central inverter or microinverters? Micro inverters are nice because they allow panel level monitoring.
 

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augustiron said:
Typical

Average annual looks like this in SF, South facing, no shade.
Click to expand...
I'm comparing Sept/Oct/Nov production this year vs last year, so that takes seasonality out of it.

Just wondering if it was a matter of just less sun this year vs last year for those 3 months.
 
My seasonal average is consistent.

It probably did have to do with the cleaning, but the Bay area is also full of microclimates so maybe that has something to do with it.
 
GAJ said:
how about you all?

Maybe it is weather related?

I'm in Santa Rosa.

Sept, Oct and Nov production vs prior year all down individually, and 20 percent as a whole.

Mind you last September I did have the panels cleaned but they don't look all that dirty at the moment.

Just wondering if I'm the only one experiencing that the past three months.

Thanks.
Click to expand...
My production for the same time period is down 19% from last year as well. Rincon Valley.

Flip
 
Going doing because of the season. I did have my panels cleaned in July. Noticed a 12% increase in production.
 
flips21 said:
My production for the same time period is down 19% from last year as well. Rincon Valley.

Flip
Click to expand...
Ah, ok thanks.

I thought it might be due to a tree next door but looking at it today I don't think that is the cause.

Just a shitty sun fall I guess.
 
I've had panels since 2015. Never wash them. Some years are better than others.
 
GAJ said:
how about you all?

Maybe it is weather related?

I'm in Santa Rosa.

Sept, Oct and Nov production vs prior year all down individually, and 20 percent as a whole.

Mind you last September I did have the panels cleaned but they don't look all that dirty at the moment.

Just wondering if I'm the only one experiencing that the past three months.

Thanks.
Click to expand...

Do you have monitoring software for your system? 20% is a drastic drop and weather changes are unlikely to cause that large a swing year over year. My assumption if I see a drop that large in one of my systems is that I have panels offline. Mind you, my experience is with larger multifamily systems, not single family, but the principles are the same.

Panels do go bad, they do break, and they do require maintenance and inspection regularly to remain functioning at expected rates.
 
Eldritch said:
Do you have monitoring software for your system? 20% is a drastic drop and weather changes are unlikely to cause that large a swing year over year. My assumption if I see a drop that large in one of my systems is that I have panels offline. Mind you, my experience is with larger multifamily systems, not single family, but the principles are the same.

Panels do go bad, they do break, and they do require maintenance and inspection regularly to remain functioning at expected rates.
Click to expand...
Yes, I have monitoring software and all panels are functioning.
 
This month has been rough for production in my area. The aggressive Tule fog has all but zeroed out any solar production. Normally, production goes down. You can see what my panels did in 2023 by month:

1765337649259.png


By the time we get to December... I'm generating for fewer hours, less effectively. As another data point to the fog, in 2024, I was pulling 25-30 kWh in early December. Now I'm lucky if I'm getting 15, with many days coming in under 8.
 
Good news is that my total electric bill for sept+oct+nov was $22.
 
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