Considering solar panels, looking for sizing/financing advice

[Electrph]

sorry no help on ID
maybe part of rack system on ur install ? .. i found quite a few screws / a few bits wire trimmings in my gutter post install .. nothing that cool
i would guess they dropped it / assumed made it to ground / could not locate it and just used another .. but my mind works similar to you ..I would want to be more sure is not something "missing" ..
i would wait see if you can find out from someone more knowledable on here than me before calling tesla ..if find out what it is exactly then u can better determine if it is missing post install

 

[willow_hiller]

sorry no help on ID
maybe part of rack system on ur install ? .. i found quite a few screws / a few bits wire trimmings in my gutter post install .. nothing that cool
i would guess they dropped it / assumed made it to ground / could not locate it and just used another .. but my mind works similar to you ..I would want to be more sure is not something "missing" ..
i would wait see if you can find out from someone more knowledable on here than me before calling tesla ..if find out what it is exactly then u can better determine if it is missing post install

It's definitely part of the racking system. Found the part on eBay: (20) Zep Solar Double Zep Groove & Interlock Zeps Key & Tongue Mounting Fastener | eBay

It's not a cheap bolt! Even in bulk, that's $3.50 per fastener.

I guess even if it is a component from my system that fell off, most of the critical things have multiple points where they're attached to the system.

 

[Electrph]

yea i seriously doubt anything like that would come off unless ripped off by hurricane etc then you would have much more damage .. i dont know your panel layout but if u are able to look under your panels im sure there is a pattern / frequency to where panels attached and you could spot if one missing and as you said redundancy to attachment points i'm sure
my money is still on dropped / or perhaps it was faulty in some way so they meant to chuck it to ground ..either way climbing down during the install job just not worth it for even a relatively expensive bolt

 

[willow_hiller]

Before and after stats coming next year!

Just realized I'm a bit late for a one year update! Thought I'd move the quote over to this thread for more relevance.

For context, solar PTO in September 2020, and upgrading from an old 10 SEER heat pump to a 20 SEER variable speed heat pump in March 2021.

March 2020: 1,016 kWh consumed
April 2020: 848 kWh consumed
May 2020: 879 kWh consumed
June 2020: 1,462 kWh consumed
Total electricity bill for those 4 months: $670.15

March 2021: 725 kWh consumed, 1,110 kWh produced (net -385 kWh)
April 2021: 463 kWh consumed, 1,116 kWh produced (net -653 kWh)
May 2021: 550 kWh consumed, 1,281 kWh produced (net -731 kWh)
June 2021: 729 kWh consumed, 1,1160 kWh produced (net -431 kWh)
Total electricity bill for those 4 months: $-13.32 (true-up at the end of March, less interconnection fees).

So an average reduction in consumption of about 40% with a new, efficient heat pump. And plenty of solar production to generate enough bill credits to hopefully cover my winter heating bill when solar production is lower.

 

[Az_Rael]

@willow_hiller thanks for the update! We have been considering going with a variable speed compressor, interesting to see the reduction in consumption.

 

[pdx_m3s]

Right on!
I'm about 9 months post-PTO and so far the system is producing more than what it was expected to. I've generated 1,200 kWh more than what Tesla and PVwatts said I should by this point. If I'm lucky, I'll generate 2MWh in July.
I'll post a 1 year update in my thread this October.

 

[Zaxxon]

I'm about to hit 50 MWh since my first system PTO. Since March of this year we've used a net of about -300 kWh from the grid. Fun.

 

[pdx_m3s]

How is your system performing in terms of what it should on paper? Tesla/PVWatts estimate...

 

[Zaxxon]

How is your system performing in terms of what it should on paper? Tesla/PVWatts estimate...

My older system (non-Tesla, installed 2014) is outperforming the original PVWatts estimate by about 3%. That called for 5,600 kWh/year. Looking just at the 2015-2020 period containing the six full years it's been on, I've averaged 5,777 kWh/year.

The Tesla system (installed 2019) called for 4,900 kWh/year (similar size in panel count, but it's on the non-ideal roof faces). 2020 is the only full year of data so far, but it also outproduced--5,159 kWh last year, or 5% overproduction.

 

[charlesj]

I think all the over production above the prediction might be because of weather pattern changes? I think PVWatts uses weather over some time averages?

 

[dareed1]

By default PVWatts assumes an efficiency of 86%, which is likely low compared to a modern system. Roughly speaking, the inverter and any optimizers will be at 97%, wire losses might be 1-2%, dust maybe loses 5%. Over time, the panels lose power capability compared to faceplate rating, but that is around 0.5% per year (again for modern panels). All together, for recently installed systems, 90% efficiency is likely to be closer to the mark than 86%. If the panels are really clean, 95% is likely.

 

[pdx_m3s]

By default PVWatts assumes an efficiency of 86%, which is likely low compared to a modern system. Roughly speaking, the inverter and any optimizers will be at 97%, wire losses might be 1-2%, dust maybe loses 5%. Over time, the panels lose power capability compared to faceplate rating, but that is around 0.5% per year (again for modern panels). All together, for recently installed systems, 90% efficiency is likely to be closer to the mark than 86%. If the panels are really clean, 95% is likely.

In my PVWatta calc, I updated the efficiency to 90%. Probably still a little low. Especially for the first year.