What makes a good Solar Panel

[Ellis Redding]

What makes a good solar panel?
There are spec-sheet properties, but I'm guessing like everything else, stats like that can be gamed.
Spec sheets also don't encompass fit and finish.
How about UL certification? Is that critical? Is it worth paying more for?

But how big of a difference is someone going to see between new mono crystaline panels say a RenaSolar going for $0.40 a watt vs a REC Solar Pure going for more than $1.00 a watt?
The difference is not trivial.

 

[sunshine_eggo]

What makes a good solar panel?

https://www.pvel.com/wp-content/uploads/2020-PVEL-PV-Module-Reliability-Scorecard.pdf

There are spec-sheet properties, but I'm guessing like everything else, stats like that can be gamed.

Not really. A better way to compare panels is to use their NOCT rating as that's more typical of real-world performance.

Spec sheets also don't encompass fit and finish.

Aside from the cheap small panels in Will's reviews, I can't recall panel fit and finish ever being an issue when dealing with panel manufacturers sold by reputable retailers (Alibaba doesn't count).

How about UL certification? Is that critical? Is it worth paying more for?

If you are installing in the U.S. where compliance with any version of the NEC is required, UL listing is a must. This likely applies to every square inch of the 50 states.

But how big of a difference is someone going to see between new mono crystaline panels say a RenaSolar going for $0.40 a watt vs a REC Solar Pure going for more than $1.00 a watt?

Depends. Some panels perform better in certain circumstances. Northern latitudes may benefit significantly from a bifacial panel that collects from both sides. In lower latitudes, you wouldn't see a difference.

Mono vs. Poly performance is rarely distinguishable from each other.

 

[BentleyJ]

The main difference with the higher priced panels is they experience less aging degradation thus have better warranties. For example, a normal, lower priced 60 or 72 cell panel would have a guaranteed output of 80% of original after 20 years of service while a high end panel like REC will guarantee 85 to 90% output for 25 years. Other benefits of more expensive panels may be higher initial efficiency ratings and less voltage drop at high operating temperatures.
We are in our 12th year of a Solar City lease and the array output (Yingli Brand) has dropped noticeably. Not to mention it was a crappy panel to begin with efficiency wise. Back then, I didn't know much of the details of solar. If I were starting over, I would be happy to pay more up front to get a better overall system that would last longer.

 

[HRTKD]

Solar panels are almost a commodity these days. I bought mine based on size, local availability, efficiency and wind load, pretty much in that order.

 

[Ellis Redding]

So, I'm kind of getting mixed messages here.
On one hand, I'm hearing that panels are a commodity, on another I have someone suggesting that buying quality would have been better at year 10.
Is it the case that panels made today are going to be better at year 10 than those from 10 years ago? Or is it just that they all look the same at year 1 and then things go south for some.



Though this suggests that 'Tier 1' is not a particularly useful title:

 

[gibbygoodtunes]

Save yourself a pile of money and get some used panels. Ask to test them if your concerned. You can even over panel a bit if they are older to make up for efficiency loss

 

[HRTKD]

On my RV, I didn't have a lot of space. I had to make the best use of what I had so I bought new panels that fit just right. If I was doing this at a house, with a ground mount, the used panels are something that I would consider. But shipping on any panel, new or used, is expensive. That's why I found a local source.

 

[Hedges]

Read the reports and select a brand/model known for reliability and durability. Unless you only plan to use for a few years.
"Never let them tell you that they're all the same."

Some panels degrade faster.
Early panels from decades ago could be high quality, unless yellowing reduces output. But they are less efficient, 100W or so per square meter. Newer ones reach 200W or so.
Some panels use cheap materials that fail. Cracking backsheets and snail trails are probably from that, maybe also environment.
Some panels (SunPower) used other type of doped silicon for less degradation in UV. But they degraded rapidly due to "PID" when in negative ground arrays. So SunPower arranged for positive-ground inverters. Newer models have greatly reduced PID.

Used panels of good quality can be a bargain.


I've had AstroPower an Sharp for about 18 years. I thought the Sharp were producing better, but eventually 25% of them degraded and the others look questionable based on IR inspection. I'm still trying to get through to the warranty department.

 

[Bvillebob]

I have both. I bought a couple of pallets of Santan's used 250 watt panels a couple of years ago. They're older panels, but I get great output from them and the price was right, no complaints. Last. year a bought 24 of the REC brand new split cell 370 watt panels from them, one of REC's best panels. The difference I see is that they're only 2 inches longer than the older 250's due to increased efficiency, and they're considerably lighter, due to improved manufacturing tech. They also produce plenty of power, no complaints. I paid about $.50 per watt for them from Santan, they were brand new. Compared to the 64 watt panels I bought 12 years ago for $5 per watt and are about the same size, I'm very happy with them....

 

[iamrich]

Price, quality, delivery... Pick two...

I think the most important variable is how much space you have. If you have unlimited space, I think used 250-300w panels are hard to beat. They are small/light enough to move with one person and inexpensive. If you have limited space, you are probably better off paying to milk every last watt out of each panel.

 

[robby]

I am lucky in that I have a Solar supplier about two miles from my house. I have gotten to know the owner and the staff very well and have gotten to play around with just about everything he sells, plus heard the owners own feelings on equipment and his field experience. At the end of the day he told me what I think @Hedges post summed it up the best. Go for a brand known for reliability and durability.

The store I was going to had lots of various panels and Inverters for sale, I bought my Sol-Ark from them and one of my EFlex batteries. After the owner got to know me he said honestly I sell these Panel brands because most people want low priced panels. If you want something really good go with LG. Now this guy does not even sell LG panels so I had to go elsewhere to get them. That was a clear indicator to me that he was being very sincere.

When my LG panels arrived I can tell you straight up that they are not like the other 3 or 4 brands I looked at in his store. Much better construction, the glass and frame feels so much tougher, the sealing of the panel is so much better and the specs for performance was a lot better.

Once up on the roof I started to compare them to a house that I pass on the way home that has some big 72 cell low cost panels on it. Those always look dusty on the surface while my LG seem to almost repel dust and stay shiny. Even if a bit of dust sticks to them, it is gone after the next rainfall and the panels are once again shiny and new looking.

Since putting mine up I have heard some horror stories like @Hedges of people not getting the same power levels from low cost panels after just 10 years. Others tell me of water leaking into the panels and other people say one or two of their panels developed dead cells.
If your just looking at the Short term then yeah go with anything that provides enough power and is sold at the best price. If your looking for that true 25-30 year lifespan your going to need top brand panels.