What is considered to be a good $/watt OTD (with all taxes/fees minus the rebate)?

[bob-n]

J.P.M. You make many excellent points. Input is impossible for us to accurately know over time. There are other degrading factors other than the panels themself, like dirt. And you say so much more that is also valid and important.

With that said, are you suggesting that the panels from one maker which claims 10% degradation over 20 years are similar to the panels from another maker that claims 20% degradation over 20 years? Or is a premium panel really better in some way?

In my business (not a solar company), our customers rely on us to measure things that they can't measure and we built our reputation on good measurements. We go out of our way to measure to traceable standards and explain the standards that we use. We use superlatives in marketing, but we don't stretch the truth in numbers.

Whether premium performance is worth a premium price is a completely different question and depends on each situation. Panels for space is an example of a particular situation. Home use is a completely different situation, as others have said. What we haven't said is what we value in a home situation. Some will value dependability - they need the system to be able to deliver a certain power level into the future. Others will value economy. They want to maximize or achieve a particular return-on-investment or or meet a specific break-even time. In addition, there is a value to low risk. How much premium are you willing to pay for things like a lower failure rate, better warranty, or long-term financially-stable supplier?

Each one of us has to make these decisions for ourselves, and needs some facts to guide us. We're hoping that we can use numbers in data sheets and other facts to help make these decisions. Are we kidding ourselves?

[Duxa]

But the things that make panels more efficient in space, still cost lots of $$ to do. Sure they can be built in that manner for earth, and they might use some of the expensive cells in a panel, but it would likely cost $300 watt . for space use, that's OK. But for terrestrial use, it's not cost effective. For every one of the high efficiency cells that make it to space, about 50 are scrapped for poor performance.
There is no "secret formula", but rather an expensive process.

Yeah, I was just saying that our needs are different than the panels that go in space, they have to worry about things we dont have to worry about, and we have to worry about things they dont have to worry about.

I do agree with what you said.

[Mike90250]

........So I dont think its fair to compare those panels to what we are doing. Completely different environment.

But the things that make panels more efficient in space, still cost lots of $$ to do. Sure they can be built in that manner for earth, and they might use some of the expensive cells in a panel, but it would likely cost $300 watt . for space use, that's OK. But for terrestrial use, it's not cost effective. For every one of the high efficiency cells that make it to space, about 50 are scrapped for poor performance.
There is no "secret formula", but rather an expensive process.

[Duxa]

Duxa:

There's made up numbers and then there are other made up numbers. Without seeing warranty claims and numbers, you have no basis for being sure of anything. Without understanding ways performance can deteriorate, you have no way of knowing if a performance deterioration rate is reasonable.

If a panel that's on you property experiences an output or efficiency drop over a period of time, how will you even know it, much less go about verifying such a condition ? Well, as a consumer, you won't in any reliable and repeatable way because you, I and every other consumer cannot even reliably measure input, or even understand it, much less deal with the intricacies of PV output and measuring it and then putting all that together and come up with an efficiency drop.

If you think you can do all that - accurately - please enlighten us all how you would go about it.

Believe what you want but if you think you can, you are mistaken. Additionally, since you need a measure of input as accurate as output, you and most every other consumer do not have access to the type and quantity or quality of historical meteorological data including site measured irradiance necessary to measure and so verify an efficiency drop.

Then, there's the whole question of measuring and recording how dirty the panels have been, how often they were cleaned and how effective any cleaning has been. Data of all such things will be necessary for any successful performance warranty claim.

Point is, while it's not necessarily a made up number, performance degradation is more an estimate based on lab measurements and projections based on accelerated aging rates and other methods than a hard number that's been field verified under varying conditions.

The main and probably only reason for things like production guarantees is for marketing. Mfgs. know more about performance degradation then most any consumer and they know verifying a performance warranty claim in the field is next to impossible, even with a lot of knowledge and equipment. So, they get to say pretty much what they want knowing performance will almost never be checked in ways required for a successful performance warranty claim.

Well intentioned but very uninformed folks like you drink the Kool-Aid marketing hype and greenwash media garbage thinking a premium paid for a panel will get extra performance and more reliability. The reality is something different. Folks who have been around for a long time with more experience and education than you know this and also know that beyond a certain level of basic quality and Q.C. panels are mostly a commodity.

Take what you want of the above. Scrap the rest.

First of, I want to say that Im not trying to argue anything. I am just trying to participate in a discussion and share my own opinion about things.

Now. I think you are approaching this from a completely different angle than I am. I do not care at all about precision measurements, they are unnecessary in this case. Things like this have a +- margin of error, always. All you have to do, as a consumer is to look at your yearly production during year 1, then if at any point in the future your year over year is significantly lower than the advertised rates you call up the warranty, its up to them to measure and prove to you that the degradation is within the expected range. Otherwise you get a new panel.

Additionally there is such thing as false advertising. And I do not think top end brands would be advertising something that was blatantly false, especially when it is so easily checked.

Now, personally, all these things aside, I would trust Panasonic, LG, and other brands that have been doing this stuff for decades, and their advertisements than some random hole in the wall place in China. Why? Well because they are operating 50 years later either because they make good products, or not one of the millions of their customers (including businesses with the proper equipment to check their claims) has ever called them out. And I find it extremely unlikely that their product doesnt match the advertisements, as it is extremely unlikely that over 50 years not one in many millions has called them out on it.

When you are buying into a company like LG or Panasonic or any other major brand, you are also buying into their warranty, guarantee that they will be around to honor that warranty, access to their service centers etc etc...

Thats just my personal opinion... participating in conversation. Not trying to prove anything. As with everything in life, you get what you pay for. There is a reason some panels are cheaper and others are more expensive. If the cheap panel could sell itself for more, then it would. Solar panels arent some new unknown technology, its older than cell phones.

[J.P.M.]

They have been making panels for nearly 50 years (since the 70's) Im sure its not just a made up number.

Duxa:

There's made up numbers and then there are other made up numbers. Without seeing warranty claims and numbers, you have no basis for being sure of anything. Without understanding ways performance can deteriorate, you have no way of knowing if a performance deterioration rate is reasonable.

If a panel that's on you property experiences an output or efficiency drop over a period of time, how will you even know it, much less go about verifying such a condition ? Well, as a consumer, you won't in any reliable and repeatable way because you, I and every other consumer cannot even reliably measure input, or even understand it, much less deal with the intricacies of PV output and measuring it and then putting all that together and come up with an efficiency drop.

If you think you can do all that - accurately - please enlighten us all how you would go about it.

Believe what you want but if you think you can, you are mistaken. Additionally, since you need a measure of input as accurate as output, you and most every other consumer do not have access to the type and quantity or quality of historical meteorological data including site measured irradiance necessary to measure and so verify an efficiency drop.

Then, there's the whole question of measuring and recording how dirty the panels have been, how often they were cleaned and how effective any cleaning has been. Data of all such things will be necessary for any successful performance warranty claim.

Point is, while it's not necessarily a made up number, performance degradation is more an estimate based on lab measurements and projections based on accelerated aging rates and other methods than a hard number that's been field verified under varying conditions.

The main and probably only reason for things like production guarantees is for marketing. Mfgs. know more about performance degradation then most any consumer and they know verifying a performance warranty claim in the field is next to impossible, even with a lot of knowledge and equipment. So, they get to say pretty much what they want knowing performance will almost never be checked in ways required for a successful performance warranty claim.

Well intentioned but very uninformed folks like you drink the Kool-Aid marketing hype and greenwash media garbage thinking a premium paid for a panel will get extra performance and more reliability. The reality is something different. Folks who have been around for a long time with more experience and education than you know this and also know that beyond a certain level of basic quality and Q.C. panels are mostly a commodity.

Take what you want of the above. Scrap the rest.

[foo1bar]

How do we get some of those technological advances into residential panels in a cost effective way over the next 10-15 yrs?

I think by the same way they've been getting into residential for past 15 years.

What was typical efficiency in 2005?
What's typical efficiency now?
And as for "cost effective" - What was the cost per DC watt in 2005? And what is it now?

[Duxa]

I know for a fact that the panels used in satellite applications are very nearly bare cells, no glass, no frame, just the wafer and an AR coating, usually on accordion folded kapton film as shipping and deployment support. And using costly exotic doping and exacting manufacturing and screening.

I would imagine conditions in space are completely different? 300C in the sun, -300C in the shade? No atmosphere to filter UV and other spectrums, as you mentioned no need to protect from anything, because if anything hits it it will hit it as such a speed that no amount of protection will save it.

So I dont think its fair to compare those panels to what we are doing. Completely different environment.

[Mike90250]

I know for a fact that the panels used in satellite applications are very nearly bare cells, no glass, no frame, just the wafer and an AR coating, usually on accordion folded kapton film as shipping and deployment support. And using costly exotic doping and exacting manufacturing and screening.

[JSchnee21]

Slide 8, Slide 15 -- Sanyo/Panasonic have been mass producing HIT panels for >20yrs. More than 4 million panels in Europe alone since 2003.

https://pdf.archiexpo.com/pdf/panasonic-solar/general-presentation-panasonic-hit/83914-303778.html

Yes, LG is considered Premium, though both have played second fiddle to SunPower for years, Though that seems to be changing. It seems like SunPower has largely come and went these days.

"Generic panels run in the area of 20% conversion efficiency, and that DOES NOT improve
with lower light levels, they quit all together before you drop to moonlight. Receiving light
at an angle means less intensity, and the preservation of energy will decrease the energy
the panel can deliver. While claims of panels working better under clouds keep being
heard, they are NEVER backed by any hard numbers. I will continue to believe any slight
ripple in the efficiency vs intensity curve, is lost in the noise for renewables. However I
have been able to achieve a 100% increase in energy my inverters get under clouds, the
old fashioned way. Double the number of panels connected to the inverters"

My point, was that it would be nice to see data as to whether or not different glazing coatings, textured cell surface structures, exotic element doping, half cells, copper clad backings, Cello, etc. and other hog wash various vendors may claim do anything at all to improve the quite poor off angle, diffuse, and low light collection efficiencies seen for all commercial and residential panels. That is to say do any of these technological innovations improve the harvest efficiency of the cells (separate from the conventional areal efficiency metric) during the 90+% of the day when the sun is not directly overhead.

Clearly it's possible to make solar cells which are much more efficiency (~46%) for aerospace applications -- though not cost effectively and not in sufficient volumes, How do we get some of those technological advances into residential panels in a cost effective way over the next 10-15 yrs?

[foo1bar]

I see people talk about saving money by getting like 270w panels instead of 325w or 330w ones, also I think its not just all about output right? Worksmanship is a big part of it?

I wouldn't say a big part.

most likely if it's going to catastrophically fail it'll fail fairly early - probably within the first 12 months.
And if it doesn't fail then, it's very likely to last until about the end of it's expected life (~20 years)
Panels like most semiconductors have a "bathtub curve" for how likely they are to fail. More at the beginning and end of life, few in the middle.

A Crysler may give you better (or same) performance as a Toyota, but Chrysler will leave you stranded somewhere due to poor worksmanship.

heh - funny you should use those as your example - I have had better luck with Chrysler than with Toyota.

[Duxa]

So, what's the difference between the standard & high output panels... about 1%
4,000w vs 4,040 watts ??

I see people talk about saving money by getting like 270w panels instead of 325w or 330w ones, also I think its not just all about output right? Worksmanship is a big part of it? A Crysler may give you better (or same) performance as a Toyota, but Chrysler will leave you stranded somewhere due to poor worksmanship.

[Mike90250]

So, what's the difference between the standard & high output panels... about 1%
4,000w vs 4,040 watts ??

[bcroe]

They have been making panels for nearly 50 years (since the 70's) Im sure its not just a made up number.

Some kind of panel has been for sale, but the 6 inch square 4W cell panels at the current
efficiency have not been around 20 years. Maybe someone has a date? Bruce Roe

[Duxa]

I really have doubts that the decrease over 25 years is much more than a guess, the
brand differences may be just advertising hype. What I would expect is that the
highest output panels would degrade more, let me know in 25 years if that is wrong.
Bruce Roe

They have been making panels for nearly 50 years (since the 70's) Im sure its not just a made up number.

[Duxa]

"the thing that makes premium Panasonic ones worth it is that after 25 years they will produce 90%, while most other brands will do 80%"
The LG Neon 2 panels advertise they will produce 90.08% after 25 years. https://es-media-prod.s3.amazonaws.c...N1C-V5_AUS.pdf

"Also I wanted Enphase system as I want to see how much each panel is producing"
SolarEdge systems with power optimizes provide individual panel monitoring at no addl. charge. https://www.solaredge.com/products/pv-monitoring#/

"Also the prime space on my roof is kinda limited, so I need high producing panels to maximize watts per sq foot."
LG has panels rated at over 400W with 20%+ efficiency. https://www.lg.com/us/business/solar-panels

Arent LG panels and ones with Optimizers considered to be premium? I wasnt shilling for Panasonic specifically, I was just justifying going with premium over cheapo ones.