Quality difference between 20c/w and 40c/w panels?

Over the last year, I've been keeping an eye on prices and availability of "panels by the pallet" from Signature Solar, with the plan to eventually purchase around 30 panels for an off-grid ground mount solar installation. I will be connecting these panels up to an EG4 18K with their indoor wall-mount battery.

I was originally planning to buy some ~500W Canadian Solar Bifacial panels for around 50-75c/w but I don't see that brand much in online retail stores anymore, at least not "by the pallet". Lately, I've been watching the Adani Solar 530w Half-Cut Mono Bifacial panels for 30c/w. They used to be sold by the pallet from Signature Solar but are now only sold individually (min 10) for 31c/w. Now I'm seeing panels with similar specs down to 25c/w, like these ones from Lumina Solar Space. And there's even these from REC at 18c/w!

Now, I understand that last one from REC is clearly not comparable in specs to the first two I listed.
But my question is, what should I look out for when determining quality of solar panels? Is it just a matter of sticking with the well-known manufacturers and paying for the brand premium? This is the first time I've heard of "Lumina Solar Space" but all the specs seem to match other solar brands (bifacial, half-cut mono, >500w). Can I generally trust that all panels sold from Signature Solar meet some kind of minimum quality?

And there's even these from REC at 18c/w!

REC new for $0.18/W sounds really good. I consider them a premium brand panel.

Price is getting low enough that price doesn't matter anymore; you are likely to spend more on mounting hardware.
What matters is how long the panels last, and how well their power output holds up.

Sign up for free, download reports for a number of years, see which brands consistently withstand stress tests without failing.

Here's a short (Australian availability) list of top performing panels

Solar Panels Comparison: Types & Brands

There are over 100 solar panel brands approved by the Clean Energy Council for sale under Australia's federal rebate scheme. As the most valuable part of
Give your contact info to download complete reports from to which includes models available elsewhere..
It doesn't say who's on the sh*t list, but it names all "top performers" for each test.

Lots of good data in these reports, and they give reason to fear poor quality panels. Don't let anyone tell you they're all the same.

Results vary. Will depend on environment and panel quality.
Most consumers will not know.

Mine were in a relatively benign environment (San Jose), and I've heard this model was known to suffer degradation.

I suppose I could buy a solar panel tester like Will reviewed, but that doesn't feel DIY enough to me.
Besides, I'm a cheapskate, and I try to do things in the most difficult (and expensive if the equipment wasn't on hand) way.

I'm presently working on an underperforming string of Sharp 165W Polysilicon. Underperforming like this 12s string is putting out about 68% the current of an identical paralleled 12s string.

I don't find Voc varying much.
Isc, lowest panel is only putting out 66% of highest.

When measuring Isc, you want to avoid arcing and burning contacts. You can use a suitable...
What is common is fade, and rate varies among panels.

How significant of a difference between a 72 cells vs 144 cell panel type ?

is it worth spending the extra $ for the 144 cells type panels ... like the one below---> that's $ different for a pallet of 31

What do i look for to compare

Lumina Solar Space 535w Bifacial Solar Panel Pallet | SS8-72HD-535M @ $0.25/w​

Philadelphia Solar 550w Bifacial Solar Panel | PS-M144(HCBF)-550W $0.335/w​

Those both have 72 wafers cut into squares and cut into 144 halves.
They are both bifacial.

Lumina Solar Space 535w Bifacial Solar Panel | SS8-72HD-535M

Upgrade your solar energy system with the Lumina Solar Space 535W Bifacial Solar Panel | SS8-72HD-535M. Available at Signature Solar for efficient and sustainable energy solutions.

Philadelphia Solar 550W Bifacial Solar Panel

Experience cutting-edge solar technology with the Philadelphia Solar 550W Bifacial Solar Panel. Available at Signature Solar. Built for durability and efficiency, this panel delivers high output with advanced Mono PERC Half-Cell technology, ideal for any environment.
Sold as singles, I see one $0.29/W and the other $0.34/W

When you buy a bunch, and when you buy other stuff, you can contact a vendor and ask for a package price.
I have a pickup to I take delivery at a freight terminal, saves a few dollars, also time.
At least one of those says shipping to a loading dock only, no residential delivery.

I don't know the names, see if they are mentioned in the reports I gave a link to.

Are you able to manage the size and weight? Have a helper?
I find panels up to about 325W ~ 370W that I've received possible to handle alone.
The 500W+ might be more efficient in labor and mounting hardware, but only with two people.

Any of these half-cut panels I expect to confuse some MPPT, but I don't have experience with them (yet). I have bought some, just not installed and operating yet. They are wired internally as 2p3s, whereas most panels are 3s. I think this does funny things to the I/V curve.
Plan your shading wisely.

Also, to answer your question, I believe half cut panels have better tolerance against shading. I don't know how effective it is, but that's what the industry marketing material says.

I figure it could help in a commercial array with multiple rows in landscape orientation.
When one row shades up to 50% of a panel, that panel's current is cut in half but voltage isn't. Judicious allocation of panels to strings could make that work well or a large system with many paralleled strings.

On the other hand, with separate MPPT per PV string, I'd rather have conventional panels. Shading of up to 1/3 loses 1/3 of voltage, up to 2/3 loses 2/3 of voltage.

Both should work for home systems, and shade is to be avoided. I do expect that shade on up to 1/2 of some panels may cause loss of nearly half of entire string's output, unless MPPT is smart enough to do full sweeps periodically.



See if they are on the CEC PV module list:


If so, compare their rated power PTC, or NOCT

Data sheet one has temperature coefficient of power -0.334%/°C, other -0.35
Both show 45C as normally operating cell temperature, I guess +20C relative to 25C ambient.
20 x -0.35% = -7% from rated power, other is close to same.
But I think CEC PTC may be more realistic. See if that is quoted.

Bifacial means even higher current and power output, but only if reflected light can reach the backside, e.g. ground mounted over white rock, or snow.

The Lumina panels are actually 144 half cut cells, if you reference the PDF spec. It's very strange (and slightly concerning) that they chose to include "72" in the panel's SKU.

Also, to answer your question, I believe half cut panels have better tolerance against shading. I don't know how effective it is, but that's what the industry marketing material says.

Those both have 72 wafers cut into squares and cut into 144 halves.
They are both bifacial.

Lumina Solar Space 535w Bifacial Solar Panel | SS8-72HD-535M

Upgrade your solar energy system with the Lumina Solar Space 535W Bifacial Solar Panel | SS8-72HD-535M. Available at Signature Solar for efficient and sustainable energy solutions.

Philadelphia Solar 550W Bifacial Solar Panel

Experience cutting-edge solar technology with the Philadelphia Solar 550W Bifacial Solar Panel. Available at Signature Solar. Built for durability and efficiency, this panel delivers high output with advanced Mono PERC Half-Cell technology, ideal for any environment.
Sold as singles, I see one $0.29/W and the other $0.34/W

When you buy a bunch, and when you buy other stuff, you can contact a vendor and ask for a package price.
I have a pickup to I take delivery at a freight terminal, saves a few dollars, also time.
At least one of those says shipping to a loading dock only, no residential delivery.

I don't know the names, see if they are mentioned in the reports I gave a link to.

Are you able to manage the size and weight? Have a helper?
I find panels up to about 325W ~ 370W that I've received possible to handle alone.
The 500W+ might be more efficient in labor and mounting hardware, but only with two people.

Any of these half-cut panels I expect to confuse some MPPT, but I don't have experience with them (yet). I have bought some, just not installed and operating yet. They are wired internally as 2p3s, whereas most panels are 3s. I think this does funny things to the I/V curve.
Plan your shading wisely.





I figure it could help in a commercial array with multiple rows in landscape orientation.
When one row shades up to 50% of a panel, that panel's current is cut in half but voltage isn't. Judicious allocation of panels to strings could make that work well or a large system with many paralleled strings.

On the other hand, with separate MPPT per PV string, I'd rather have conventional panels. Shading of up to 1/3 loses 1/3 of voltage, up to 2/3 loses 2/3 of voltage.

Both should work for home systems, and shade is to be avoided. I do expect that shade on up to 1/2 of some panels may cause loss of nearly half of entire string's output, unless MPPT is smart enough to do full sweeps periodically.



See if they are on the CEC PV module list:


If so, compare their rated power PTC, or NOCT

Data sheet one has temperature coefficient of power -0.334%/°C, other -0.35
Both show 45C as normally operating cell temperature, I guess +20C relative to 25C ambient.
20 x -0.35% = -7% from rated power, other is close to same.
But I think CEC PTC may be more realistic. See if that is quoted.

Bifacial means even higher current and power output, but only if reflected light can reach the backside, e.g. ground mounted over white rock, or snow.

@Hedges
I first thought that the lumina are 72 cells but that's not correct and it sound like the panels are similar except for 535w vs 550. So $ for value, would you recommend the Lumina ? its $ different for the pallet of 31.

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