Compare modules, not cells
Efficiency is the share of sunlight a panel turns into electricity, measured across the whole module. It matters most when roof space is tight. If you have plenty of roof, price per watt and warranty usually matter more. Rated watts are measured under standard test conditions (1,000 W/m² of sunlight at 25 °C cell temperature), so they are a yardstick, not continuous real-world output.
Watts are not efficiency. A bigger panel with a bigger watt rating can be less efficient than a smaller one. Compare watts per square foot, or use the roof-fit calculator, which works efficiency out from size and watts.
What you can actually buy: documented examples
These rows are real product families taken from manufacturer datasheets. They are examples of each technology, not market averages, and a given wattage may not be in stock. Always confirm the exact model your installer quotes.
| Technology | Example | Module efficiency | Power |
|---|---|---|---|
| Mono PERC | Mission Solar MSE PERC 108HC | 20.5–21.0% | 400–410 W |
| TOPCon (n-type) | Qcells Q.TRON BLK M-G2+ | up to 22.5% | 415–440 W |
| TOPCon (n-type) | Canadian Solar TOPHiKu6 (sampled models) | 21.3–23.5% | varies by model |
| Heterojunction (HJT) | REC Alpha Pure-RX | up to 22.6% | 450–470 W |
| Back-contact | Maxeon 6 (US residential datasheet) | 22.0–22.8% | 425–440 W |
| Thin-film CdTe | First Solar Series 6 Plus | about 18.1–19.0% | 455–480 W |
| Flexible mono silicon | Renogy 100 W flexible | 15.7% | 100 W |
Two caveats. The Canadian Solar range spans several product families, so its top end is not one panel. And the REC lower bound is not published, so we do not state one.
Which type fits which roof?
PERC
The older mainstream design. It is still catalogued, and can make sense when a verified quote is cheaper and you have enough roof. The trade-off is lower power density and, in the example above, a steeper warranted decline (see lifespan and warranty).
TOPCon
The current mainstream choice for new rooftop systems, with high documented efficiency and long performance warranties. "TOPCon" on its own tells you little: compare the exact model, its temperature coefficient, warranty exclusions and delivered price.
Heterojunction and back-contact
These sit at the premium end for roofs with limited space or hot summers. Whether the extra output justifies a price premium only shows up by comparing like-for-like quotes. For back-contact, verify the US model, the authorized seller, and which company stands behind the warranty.
Thin-film (CdTe)
Proven commercial technology, but First Solar's product documentation addresses large installations. We could not confirm an ordinary homeowner purchasing channel, so we do not list it as a readily available residential option.
Flexible panels
Flexible describes how the panel is built, not what chemistry it uses: the Renogy example above is monocrystalline silicon. It suits curved or weight-sensitive surfaces such as RVs and boats. Expect lower efficiency and a shorter warranty than rooftop panels, and follow the mounting instructions (the maker says not to walk on it).
Bifacial: a feature, not a technology
Bifacial modules collect light on both faces. The rear gain depends on mounting height and what is below the panel. Ordinary close-mounted sloped roofs leave little room for rear light, so no universal percentage bonus is defensible. Bifacial is more relevant on raised ground mounts, reflective surfaces and some off-grid setups, per the U.S. Department of Energy's Solar Futures Study.
Lab records are not products
Headlines about "35% solar panels" describe research cells. LONGi announced a 35.5% perovskite-silicon tandem cell on July 15, 2026, and says it was certified by ESTI; we have not inspected the certificate. By comparison, the one commercial tandem module shipment we could document (Oxford PV, 2024, to a US utility customer) reported 24.5% module efficiency. Cell results are measured on small areas under ideal conditions and cannot be ordered for a roof. For the full picture, see the perovskite and tandem tracker.
Quick answers
What is the most efficient solar panel I can buy for my home?
Among the US residential datasheets we checked, the highest documented figures were around 22.6% to 23.5% (REC Alpha Pure-RX and the top Canadian Solar TOPCon bin). That is a snapshot of examples, not a ranking, and availability varies by installer.
Is TOPCon better than PERC?
TOPCon examples show higher documented efficiency and gentler warranted degradation than the PERC example here. Whether it is better for you depends on delivered price, roof area and the specific warranty.
Are flexible panels thin-film?
Not necessarily. Flexible is a construction format. The flexible Renogy panel we checked uses monocrystalline silicon cells.
Do bifacial panels produce twice as much?
No. Rear-side gain depends on installation geometry and reflected light, and close-mounted roofs get little of it.
- Mission Solar PERC 108HC datasheet
- Qcells Q.TRON BLK M-G2+ product page
- Canadian Solar TOPHiKu6
- REC Alpha Pure-RX product page
- Maxeon panels and US datasheet
- First Solar Series 6
- Renogy 100 W flexible panel
- U.S. DOE: standard test conditions and performance
- U.S. DOE Solar Futures Study (bifacial)
- LONGi 35.5% tandem cell announcement
- Oxford PV commercial shipment announcement