485w Bifacials on dark shingle roof ... in THIS case

[dubjeeno]

Consider this situation : In the attached image, you will see a layout of ~400watt 72"x42" modules. Notice the 4 landscape arranged modules. Also note that the entire arrangement is 18" from the ridge. It is likely that the local jurisdiction will require 36" from ridge, in which case the landscape panels will not fit. To better utilize the same left-to-right roof space, I could either do two rows of 5 landscape and fit 10x400watt (4000w) on either side of ridge, OR do a single row of 9 485watt bifacials (4365watt) on either side of ridge. In addition to the increased rated wattage, the installation would consist of only two mounting rails, versus 4, per side.

I was recently made aware that the rating for bifacials is commonly the rating for the front face, so while I know that generally I wont get much, if any, rear side generation on roof mount on shingles, is there any reason NOT to use the 485watt bifacials. Cost per watt is actually cheaper per watt for the bifacials, with Q.Cells 405 at $234.00 ($0.58/w) and Q.Cells 485 BFD at $230.00 ($0.48/w).

So my question is .... are there any reasons not to go with the 485w bifacials in this case?

Some possible negative points I have seen tossed about include:
1. Need to ensure wiring sizes accommodate full possible output of panel (front an back) to meet code, despite never needing it due to no real rear production.
2. Possible reduced performance due to higher panel temps, due to more light passing through the glass backed panel increasing the them between panel and roof (although I have seen posts to the contrary due to better heat dissipation from double glass, versus glass with plastic backing).
3. Oddly, these specific panels only have a 12 year mechanical warranty (but still 30 year on output).

Q CELLS Q.PEAK DUO XL G10 BFG - 485 Watts | EnergySage

All you need to know about the Qcells Q.PEAK DUO XL G10 BFG - 485 Watts solar panel including rating, cost, efficiency, and warranty terms.

www.energysage.com

 

[G00SE]

Just a heads up. It may not be quite the right wattage, but dimensions similar, signature solar has bifacial panels for 26c/watt

 

[millsan1]

I went with bi facials on my roof. At the time, the bifacials were cheaper than mono facials, so I figured, why not?

 

[dubjeeno]

I went with bi facials on my roof. At the time, the bifacials were cheaper than mono facials, so I figured, why not?

Any issues to report? How long have you had them up there?

 

[millsan1]

Any issues to report? How long have you had them up there?

Just since November. No issues.

 

[rhino]

The only thing to watch for with bifacials (at least the ones I've looked at) that many people don't realize is they use thinner glass. I assume this is to keep the weight down because you have another entire sheet of glass on the back as well that adds a lot more weight then some plastic encapsulant. Most bifacials I've seen use 2mm thick glass whereas it is fairly easy to find 3mm or thicker glass on mono-facial panels. Assuming these are all tempered heat treated glass, the thicker glass will obviously be more robust especially for areas that may be prone to hail.