Every panel on a pallet is a sheet of silicon cells doing the same job the same way. The type names on the box (mono, PERC, N-type, bifacial) describe small differences in how the cells are built, and those differences show up in exactly four spec-sheet lines: the temperature coefficient, the degradation schedule, the warranty, and whether the back of the panel makes power. Read those four lines and you can judge any panel a salesperson puts in front of you.
Mono won, and poly left the building
A solar cell is a slice of silicon crystal. Monocrystalline cells are cut from a single grown crystal, so electrons move through them with less to trip over. Polycrystalline cells are cast from many small crystals fused together, cheaper to make and a little less efficient. Poly dominated a decade ago on price. Then mono manufacturing got cheap, and poly all but left the residential market.
Every panel covered in this guide is mono. If you are shopping poly today, you are shopping the used market, and used panels get judged on price per watt and condition, a different conversation entirely.
PERC and P-type: the workhorse
The Canadian Solar 395W panel on our shelves is a Mono PERC panel, and PERC is worth one sentence of translation: a reflective layer on the back of the cell gives light that got through the silicon a second pass. PERC cells are built on P-type silicon wafers, the older and cheaper recipe.
What the datasheet actually says about this panel: 395W at standard test conditions, 20.2% module efficiency, 108 half-cut cells, a temperature coefficient of -0.34% per degree C, and a degradation warranty of no more than 2% in year one, then no more than 0.55% per year after, on a 25-year product warranty.
That degradation line matters more than the wattage. At those rates the panel is warranted to hold roughly 85% of its rating after 25 years. Every serious manufacturer publishes this curve. A listing that shouts the wattage and hides the curve is telling you where to look.
N-type: the newer recipe, and what it actually buys
The SolarSpace Lumina II in our files is an N-type bifacial panel, 570 to 595W depending on bin. N-type means the base wafer uses the other doping polarity, which sidesteps the light-induced degradation that eats P-type cells in their first year, and loses less output as the panel heats up.
You do not have to take the physics on faith. Both effects sit right on the two datasheets, side by side. Temperature coefficient: -0.34% per degree C for the Mono PERC, -0.29% for the N-type. First-year degradation: 2% warranted against 1%, then 0.55% per year against 0.4%. The N-type sheet warrants 87.4% of rated power at year 30, five years past where the PERC warranty ends.
Is that worth paying for? Run the number instead of feeling it. A panel on a Florida roof runs hot, call it 30 degrees over its rating on a summer afternoon (that is a rule of thumb, so field verify against your own site if you want to be exact). At that temperature the PERC panel gives up about 10.2% of its rating and the N-type about 8.7%. On a 395W panel the gap is roughly 6W per panel at the hottest hour. Real, small, and it compounds with the slower degradation over 25 years. N-type is genuinely better. It is not twice-the-price better, and the price gap is what decides it.
Bifacial: real physics, situational payoff
Bifacial panels have cells that work from both faces, with glass on the back instead of an opaque sheet. The SolarSpace datasheet publishes the numbers: 80% bifaciality, and a rear-gain table showing the 575W bin making 604W with 5% rear-side light and up to 719W at 25%. The Waaree 585W panels we sell by the pallet are bifacial too.
Here is the honest part the ads skip, and it is geometry rather than a spec. Those gain numbers require light actually reaching the back of the panel. A ground mount over pale gravel, a pergola, an elevated rack over concrete: real rear light, real gain. A panel flush-mounted a few inches over dark asphalt shingles gets almost no rear light, so a bifacial panel on a typical roof earns close to zero of its advertised bonus. Bifacial is a real technology whose payoff depends entirely on the mounting. Buy it where the mounting deserves it.
What is marketing
Spec-sheet lines worth reading every time: rated watts, the electrical table (Voc, Isc, Vmp, Imp), temperature coefficient, the degradation schedule, both warranties, max system voltage, and max series fuse rating.
Lines that are mostly marketing when aimed at homeowners:
Cover-page slogans. The Canadian Solar datasheet cover says "MORE POWER" in giant type. Fine words. The tables below them are the product.
Efficiency, most of the time. A 20% panel and a 23% panel rated the same watts make the same energy. Efficiency only buys smaller area per watt, so it matters on a tight roof and barely matters on a barn or a field. The SolarSpace panel's 23% headline is real, and it is also simply a bigger panel, which is most of how a 585W panel happens.
All-black styling. Customers like the look, it is a legitimate preference, and it is an appearance line, no more.
Bifacial gain percentages quoted without a mounting story, per the section above.
What this looks like on a real roof
Say you want roughly 8.7kW on a metal roof. With 395W panels that is 22 of them. With 585W panels it is 15. Fewer, bigger, heavier panels mean fewer attachments and less rail time, and each panel is bulkier on a ladder, and the string math changes completely. Panel choice is a labor and design decision wearing a wattage costume. If you want to see how the options price out on your own house, build a system and swap the panel choice on the review screen.
Sources
- Canadian Solar HiKu6 All-Black CS6R-MS-HL Datasheet, v1.1C25 (August 2022)
- SolarSpace Lumina II SS8-72HD 570-595N Datasheet, version US 202412