Tell me why PV systems are not a scam

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peter d said:
Just a quick aside to this discussion - solar panels are abysmally inefficient. 20% efficiency is about all you can expect.
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I don't see what that has to do with anything, the unharnessed sun isnt hurting anything ;) Cost per watt hour of production is what matters. Internal combustion engine is a bit better, around 30%, but still abysmal. I don't see people not driving.
 
peter d said:
Just a quick aside to this discussion - solar panels are abysmally inefficient. 20% efficiency is about all you can expect.
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Show me something better at turning light into another form of energy. Plants are only about 1% efficient.

Your statement is basically wrong; it reflects a poor understanding of the meaning of the number in the context of what is being talked about.
 
Coppersmith said:
I am not a solar PV system expert at all. I have very limited knowledge in the area. But I am concerned that people are being scammed by installers of roof mounted residential solar power systems. Please correct me if I am wrong.

I say this because people are paying many thousands of dollars for systems that can't possibly produce that much power. Even if somebody else is subsidizing the system like the Gov't or the utility, they don't make economic sense for the individual and even less sense for the taxpayer or ratepayer.

It's my understanding that solar panels produce the most power when they are directly facing the sun (exactly 90 degrees). The amount of power produced falls off greatly as the angle changes from 90. The best systems track the sun keeping the panels in proper alignment as much as possible. Cheaper ground based systems don't move, but are at least aimed to maximize the potential sun input. Then there are residential systems that are built on people's roofs (usually flat to the roof). The roof could be way out of alignment with the sun and a solar contractor will put panels there anyway.

It's also my understanding that if any portion of any panel in a string of panels becomes shaded, this significantly reduces the output of the entire string, yet I see panels installed near chimneys, antennas, trees, and other things that throw shade at some point during the day.

In my travels I have seen many PV systems installed at my clients homes. The vast majority of them are backfed to the panel on a 2 pole 30 amp breaker. This must mean that the PV system produces less than 30 amp at its peak. Since the peak is only a few minutes each day, I suspect that most of the rest of time it's producing far less: 15 amps?, 10 amps?, 5 amps? And of course, the system produces zero amps at night.

A thirty amp breaker is probably what the system manufacturer requires, but since most systems are not installed to maximize solar input as I mentioned above, they are probably producing far less.

Is 15 amps of solar power for a couple of hours each day worth $10-20K in expense? And what if the roof needs replacing and all the panels have to be removed and reinstalled? And what if an inverter craps out and you have to replace it? I hear many clients talking like they are going to power their entire house off the system and sell gobs of power back to POCO. Then they wonder why it's not working. Were they oversold?

If homeowners want to create an aura of "greenness" around themselves, then fine. Otherwise, in my humble opinion, it doesn't make sense. I'll stick to recycling and bringing my own bags to the grocery store.
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I think you received some good replies on this. I think you would be surprised how much energy you get even on a cloudy day.

To sum up, one doesnt install, say, 30 - 300 watt panels and say "look you have 9000 watts!" A site analysis is done and run through software such as PV watts. It takes into account all the things you mentioned: less than ideal angle, shading, weather, latitude, losses, inefficiencies....and provides a very accurate figure for energy production. I would guess there is very little dishonestly in production numbers. I think if there is dishonesty, it would be in the payback figure being artificially low for the reasons I mentioned in post #2. Yes there are bad apples out there. How much shoddy "regular" electrical work have you seen? It happens everywhere.

I am, sort of with you on roof mounts, particularly on shingled roofs. If there is space, I would strongly recommend ground mount over roof. If you have to do a roof, I would do it on a standing seam roof with the standing seam clamps (no penetrations).
 
electrofelon said:
They may be but that's political. Let's just talk about what our experiences are with payback figures, ROI, etc. I don't see that it is productive or allowed here to debate tax credits, net metering etc.

Right now a partner and I are working on a low cost ground mount system. We went through and looked at were the costs we and figured out how to reduce them. Racking and proprietary hardware is a big one. We have things down to a 6 year payback, not counting cost of borrowing , so yes this has all beem carefully and honestly figured and isn't just something I "think".

Btw, yes of course cost of borrowing should be included in the analysis, but it's pointless for me to try to do some "wealth management analysis" and come with a figure. I tell the client to come up with that.
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jaggedben said:
No doubt there are scammers and unscrupulous sales people out there. However, you would be wrong if you think all solar systems are a scam.



That's highly vague and falsely generalizing. The economic sense depends, of course, on the price being paid to the utility for the electricity, and the state regulations that govern backfeeding the grid. Where you are, in FL, the payback on solar may be sufficiently long-term so as not to make economic - as opposed to environmental - sense. Note there are other motivations besides money to go solar.



This is misleading, especially your use of the word 'exactly'. Power falls off roughly as a cosine function. So, for example, angles within 45 degrees of perpendicular would still get roughly 70percent of the power. Because of this, the maintenance of trackers has turned out to usually cost more than the extra energy is worth. That's become more true as solar module prices have fallen.




With the advent of micro-inverters and optimizers - aka Module Level Power Electronics (MLPE) - which maximize production from individual panels, that comment is a few years out of date.



Yes, in the right market. Well, you're not really asking the question the right way. The question to ask is 'what is the levelized cost of electricity from solar', i.e. cents/kWh, and the answer, for residential in the US, is about 8cents per kWh, give or take depending on the house details and shade. (For commercial and utility scale solar it's much lower.)

BTW, I bet if you measure the amp draw randomly on different houses, you'll find 15A is not far off from average. Well, at least here in California.



It's a good idea to make sure the roof will last the life of the solar system. Many roof systems do last a lot longer. In some cases the cost of removing and re-installing is paid for by the savings.



You replace it. This is not a humongous percentage of the overall cost, especially on larger systems.




As stated elsewhere, markets vary, a lot. But looking at California, your investing up front on a 25 year timescale in which you'll make a 200%-300% return. Add in the tax credit and it's more like 400%. And it's very low risk. That's a fairly competitive investment.
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MAC702 said:
But I thought the Sun never set on the British Empire!
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Q: And do you know why the sun never set on the British Empire?












A: It didn't trust it.

Sent from my XT1585 using Tapatalk
 
jumper said:
And once again no one thinks about poor little Wales.

At least you guys are represented on the British flag. No cross of St.David last time I checked.
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Good point.
Mine was that many think of UK as just England. Indeed, call it England.
 
jumper said:
Yeah, a lot of ignorance on this out there. Not me though.

Like I am part Welsh. I would never think of calling a Scotsman an Englishman, nor do I like people to call me English.
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Understood.......British would be OK. If that's what you are.

A tale.
I was in the far east for about eight months. I had to go the local police station to get an ID card. Nationality?
They had no word for British, far less Scots. So I was labelled "incoren". English.
My wife would be "mecoren"
 
I' married to a red headed green eyed full Scott

There are some things you learn NOT to bring up

Mel Gibson for one....

sheesh

~RJ~
 
jaggedben said:
No doubt there are scammers and unscrupulous sales people out there. However, you would be wrong if you think all solar systems are a scam.
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I specifically said "roof mounted residential systems". I think ground based systems are fine as long as they are installed in open fields (no shading).

jaggedben said:
This is misleading, especially your use of the word 'exactly'. Power falls off roughly as a cosine function.
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I said "solar panels produce the most power when they are directly facing the sun (exactly 90 degrees)." If the panels don't produce their maximum output at exactly 90 degrees, then when do they do it? As far as how the power level falls off, a cosine function sounds less drastic than my understanding so you have made me feel a bit better about that.

jaggedben said:
It's a good idea to make sure the roof will last the life of the solar system. Many roof systems do last a lot longer. In some cases the cost of removing and re-installing is paid for by the savings.
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jaggedben said:
... your investing up front on a 25 year timescale ...
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Here in Florida, a typical shingle roof with 25 year shingles lasts 15 years before requiring replacement. So if the homeowner replaces the roof before installing the PV system (and that's a big if since I suspect many would not be inclined to replace a 5-10 year old roof) then you would still have to remove and reinstall the 25 year PV system when the roof requires replacement, possibly twice during it's lifetime.

Tile and metal roofs last much longer and if the system is installed on one of these it's less of an issue, however, these kinds of roofs are not typical on middle income housing. They are present mostly on high-end (i.e. expensive) houses.
 
Hadn't thought about the roof replacement cycle wanting to correspond with the PV replacement. Here, I think we WANT them on the roof if we can, because, hey, that's a lot less sunshine hitting the roof and heating the house.
 
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