Solar Panels for my home

Congrats !

Welcome to the world of ~ 4 cents a kWh electricity and ~ 1 cent per mile EV driving. All you had to do was agree to stop polluting and supporting OPEC.

 

40 total / 225 watt panels - 20 on each gable. System is 8 kW's AC "Rated"



Do prior posts understand what ""Rated" means? Several posts above say, "3.5kW's" or "7.1kW's" etc. There's a dishonesty aspect that much of the solar industry does. They give you a system output number that's simply not real.

Consider our 40 panels & their "rated" output. ........ would you come up with 9kW's? (225 watts X 40 panels) NO! That 9,000 watt number is DC, & that DC power has to go through inverters, which causes loss, & many days are cloudy which cuts the average rating, & many days are super hot, which cuts the rating, & most people don't have a tracking system to keep the sun perpendicular to their system, & that cuts the rating, & panels that are a decade or 2 old will be less efficient ...... & living far north or south of the Equator will decrease your azmyth which decreases a panels efficiency, & then different seasons will lower the asmuth AND shorten length of days, further decreasing efficiency - & you don't get the max output at sunrise & sunset as you do midday .... so all those variables mean a non perpendicular azmyth decreases your efficiency/rating as well.

But the reseller just wants to make you feel good with a big giant "solar number", & few installers will mention DC versus AC rating that systems averages from season to season & decade after decade. When our system was new, it may have averaged into the 8.1KW level, but as we get deeper into our 2nd decade, we'll likely be generating a daily average of 7.8kW over all 4 seasons. Anyway that's only about half of the convoluted formula that the industry uses - but seldom mentions.
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There are two ratings in common use. STC and PTC. The latter is a better fit for rooftop solar that typically does not match the angle to the latitude.

You are right though, ratings are one thing and what you produce is a YMMV. This is why I prefer to talk in units of kWh per Year*watt. PVwatts gives the number although it should be realized that local shading issues would change the result.

 

When I state my system AC rating, I don't include any of that stuff, but merely give the sum of the nominal AC ratings of my inverters, all of which are a bit lower than the DC ratings of the panels feeding them. I.e. my system is 7kW DC, 6 kW AC. The AC rating is what the wiring and breakers are sized for, and what the utility needs to know for its system allowances, because this is how much the system tops out at under the best conditions. Maybe that is frequent in your area, but it is not in mine.

Everything else you mention should be rolled into the annual output figures or metrics, such as annual kWh per rated watt. This varies drastically with local weather, among other things.

 

My system is under a year old but so far but I been amazed by the minimal losses from DC output to AC meter, running just over 1%. This is with SolarEdge optimizers and inveter and about a 100 feet run from panel to inverter.

 

could you share the location and the name of the company please.Thanks

 

from all data i can find - 1% (99% efficiency) inverter loss is inexplicable.
Discover the simple reasons your 5kW solar system output is too low.

It'd be great if there are links that indicate to the contrary. That said - our contractor broke down exactly what production to expect over the long haul, which turned out to be really accurate .... 40kW hrs per day.
Much less, every January/February & much more every june/july ..... monthly averaging 1,200 kWh's. Technically this MORE than zeros out our usage, but the utility company games the system, of course. The Surplus months only render a paltry 2.9 cents/kwh, whereas the shortfall months? we get charged at Tier 1 rates, costing us 5X as much. Maybe time for the Tesla powerwall?
No complaints though, as even w/ 2 plugins, with the solar (& the occasional supercharger usage) the PV paid for itself by year 7, & there's no more fuel cost.
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As in ... wrong ?

Perhaps. I was going by the data reported by the system like this photo shows:
I divide the AC power into the sum of panel DC power. I've checked this way perhaps 5 times since installing the system. This screenshot is from 11:45 am today -- I didn't tally it up ;-)



FWIW, the manufacturer spec sheet also says 99% CEC weighted efficiency.

 

Expert Residential and Commercial Solar Installers | SolarNorCal, LLC . They have great reviews and located at Sacramento area. I am using PG&E, usually quote is high. If you are with SMUD, quote could be even lower.

 

@hill

I was mulling over your post that panel ratings are far from actual and know why you say this but it is no different that EPA fuel economy ratings in the sense that operating conditions are usually different than test conditions.

Fwiw, my STC rated panels are 315 watts but I have seen 330 watts. No magic -- just a colder day than test conditions.

 

yea I don't pretend to get the whole optimizer thing, other than they help efficiency, & what that same article above says;

but obviously they are Incorporated because they help. Congratulations on the very high efficiency system!!

Same here! We've noticed the same phenomena. If we lived in Denver (cool AND sunny), that might occur more frequently, rather than right after the Sun comes from behind clouds.
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The spec sheet I posted above is for the inverter, not the optimizers.

I think the bottom line for my system is that I do not have a way to verify the information that is being reported. I think we both agree though that the system is highly efficient and the inverter quite remarkable.

However, if you are so inclined ...
The snapshot I posted above was at 12 Noon, my panels are due South, it was 70F and the sun was 18 degrees above normal. If my arithmetic serves, that implies 299 watts per panel before taking temperature differences into account. If the system software is lying, it isn't by much.

 

My co-op is much fairer in that regard: they pay 4.1 cents a kWh for excess generation but the accounting is yearly in April.
On the other hand, like everybody else I pay $32 a month just to be connected to the grid.

 

no doubt! System efficiencies get better & better all the time - as do the individual cells in new panels. Maybe it's just a pet peeve - but the industry seems to want to bolster an owners' system rating by stating it in a DC high number. Less common they rate 'em via AC.
That's ok ..... but why not provide a daily or even hourly average - based on outputs that factor all variables .... short winters/clouds/long summers/heat/low morning/evening output, etc. At LEAST as a fun fact!
As mentioned in a prior post - our daily output becomes 40kWh when factoring all daily highs/lows seasonal highs/lows .... which ACTUALLY averages out to 3 ⅓ kWh per hour, from sunrise to sunset. Maybe contractors fear that as too puny a number to mention, but they ARE able to provide it. Yea, maybe only yours truly wants that #.

If you know, for example, your average daily yield is 40kWh (ie; 1,200kWh month), & your daily average plug in use is 20kWh at home - you know you'll have 600kWh a month for home use if you want to zero out the electric bill, just using your home's lights TV fridge etc. This has been a presentation of PV fun facts.
ok here's that last one;
if you're out of roof space there are companies that retrofit water jackets to the back of panels. This not only increases panel efficiency by capturing hot water for home use ... it keeps panels cool, which raised their efficiency ... a double whammy! The company below actually sells the panels already installed.
2-in-1 solar - DualSun
pretty sweet.


it's been a while since i searched for the US/retrofit companies, but they're out there. For PHEV owners ... this is what you call, "future proofing" .... BIG time.
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So if anyone is interested in looking at what people using solar panels generate in your area SolarEdge has a website.
https://monitoringpublic.solaredge.com/solaredge-web/p/home/public?locale=en_US
This site can be searched by location and zip.

I have 26 SolarWorld 295 watt panels and 8 Panasonic Hit 325 watt panels and all my electrical needs are fulfilled with 10275 watts DC.

Next will Be a Tesla Powerwall

Blue

 

We haven't had our "7.2 kWp" up'n'running long enough -- just over six months -- to have any TOTAL "excess generation" (over the "life" of the system), but our solar array HAS produced more kWh than we "consumed" over the last two months... and so, at the risk of angering you and others who pay that $32 per month for simply being connected to the grid, I'll state here that our LAST electric bill was $10.06 (*), and our NEXT one -- which we should receive by the end of the week -- will likely be the same....

PS: A while back, I mentioned the fact that our neighbor to the south has a VERY large tree which shades our thirteen south-facing panels quite a bit (maybe up to 80% shaded) through MUCH of the the morning (see photo... taken at about 10:00 am in mid-September) for about six months out of the year, but about three weeks ago, our neighbor had the tree CUT DOWN! And WOW... THAT has made a HUGE difference in our system's kWh production through the morning hours!!!

(*) That $10.06 is broken down as follows: A "standard" residential-rate connection fee (for being on the "grid") of $9.60, and IN state sales tax of $0.66....

 

NIce system, @Son of Gloin
No anger here, since I pay the same as my neighbors do for a connection. Rather than fret about it, I just accept the cost as one related to being served by a utility that spans a rural area.

 

I'm still convinced that the absolute best (and cheapest) way to install solar on your roof is to purchase the components yourself, then hire a local electrician with solar experience to install it if you can't do it yourself. www.sunelec.com has the lowest prices I've seen for components and also package complete systems with design assistance. (if I knew then what I know now......)

Around 12 years ago I went with a solarcity 6.8 KW DC leased system. 4 years ago I purchased a new house and thy moved it for me for around $2000, repaired the old roof, and I renegotiated the lease to eliminate the lease escalation. At the time, solar panels were very expensive. I researched and the best price I found for the panels they spec'ced was $1100 each. Now, it is fairly common to pay MUCH less than $1/watt. And if you can pick it up in a trailer or box truck, you can save shipping. Enphase or PowerOne micro-inverters are around $150 to $250 each and would be the way I would go now. I'm told that installation and permitting would be around $1-$2/watt. If your handy, and have some friends to help, you CAN install yourself. If you have a tile roof, it's much more difficult.

I have no business relationship with Sun Electronics other than buying the system I installed on my RV.

 

As a low IQ, one thumbed monkey who did the DIY, I can affirm what you say: a little sweat equity saves a lot of money.

Regarding inverters though, I have to say that I am delighted with my SolarEdge choice. It is a hybrid DC optimizer at the panels with a simplified central inverter for DC to AC conversion and transformer duties. MUCH better system efficiency.

 

I don't think you understand electrical losses, or there is something unusual about your system. There is no way the described system would be 99% efficient if it were typical. Maybe the inverter is rated for 1% loss, but DC power over 100-feet of conductor on the supply side of the inverter? No way unless you are running wire the diameter of a kosher hot dog or the DC power is supplied at very high voltage.

Do you know why Nikola Tesla won out in the power market with AC against Thomas Edison's DC systems? Line loss. You would need a power generation station every block with DC.