What is the difference between PERC and TOPCon solar panels?
The difference is the cell's base material and how the back of the cell is built. PERC (Passivated Emitter and Rear Cell) uses a P-type silicon base and adds a reflective passivation layer on the rear that bounces unused light back into the cell for a second chance at absorption. It was the standard residential cell from roughly 2017 to 2023. TOPCon (Tunnel Oxide Passivated Contact) uses an N-type silicon base and adds an ultra-thin oxide layer (about one to two nanometers) topped by a doped polysilicon layer on the rear, which lets electrons through while blocking the recombination losses that waste power in a PERC cell.
Both are monocrystalline silicon, so this is not the old monocrystalline-versus-polycrystalline split; it is the next layer of detail inside the mono family. For that bigger-picture distinction see monocrystalline vs polycrystalline, and for how a cell turns light into current in the first place, see what is a solar cell. The practical upshot of the TOPCon design is lower electrical losses, which show up as a point or two more efficiency and better behavior in heat and low light.
Is TOPCon better than PERC?
Yes, TOPCon is better on the numbers, but the margin is modest. A TOPCon module runs about 22 to 23% efficient against 20 to 21.5% for a mainstream PERC module, so for the same roof area you get a little more power. The N-type base also sidesteps the boron-oxygen defect that causes light-induced degradation in P-type PERC cells, so TOPCon panels lose less output in year one (about 1% versus 2%) and degrade more slowly after that (around 0.4% a year versus 0.55%). Many TOPCon panels now carry a 30-year power warranty instead of the usual 25.
TOPCon also has a better temperature coefficient, around -0.29 to -0.30% per degree Celsius versus about -0.34% for PERC, which means it gives up less power on a hot roof, where panels spend much of a sunny day. And its bifacial gain is higher, roughly 80 to 85% of front-side output from the rear versus about 70% for PERC, which matters on a ground mount or over a reflective surface. See bifacial solar panels for when that rear gain is real and when it is not.
Does the difference matter for a home rooftop?
For most rooftops the difference is real but small, and it should not be the thing you obsess over. A point or two of efficiency changes how many panels fit in a tight space, but on an average roof with room to spare it changes your annual production by a few percent, not enough to feel on the power bill. The slower degradation and better heat performance are genuine long-term wins, but they are measured in single-digit percentages over 25 years.
What matters more than the cell label is the brand, the warranty terms, the price per watt, and the quality of the install. A well-priced PERC panel from a solid manufacturer with a strong warranty beats an overpriced TOPCon panel every time. Size the array to your actual usage with the solar panel calculator and compare real panels in best solar panels, where most of the current top picks already use TOPCon or heterojunction cells. Do not pay a large premium just to see TOPCon on the box; by 2026 it is often the cheaper option anyway.
Where does HJT fit in?
HJT (heterojunction) is the premium tier above both. It wraps the silicon in thin layers of amorphous silicon for even lower losses, reaching the highest efficiencies you can buy (about 22.5 to 23%-plus in production modules) with the best temperature coefficient and the lowest degradation. SunPower's back-contact Maxeon line and a few specialty brands use it or related designs.
For a buyer the ranking is simple: PERC is the outgoing value tier, TOPCon is the new mainstream, and HJT (or back-contact IBC) is the premium. Most homeowners land on TOPCon because it hits the sweet spot of efficiency and price, with HJT worth the premium only when roof space is very tight or you want the lowest possible degradation. For the full tour of cell generations, see what is a solar cell and solar panel efficiency.
PERC wins on
- +Cheaper per watt, and often on clearance as factories convert lines.
- +Mature, proven design with a long field track record.
- +Efficiency and output are plenty for most roofs with normal space.
TOPCon wins on
- +Higher efficiency, about a point or two more per panel.
- +Better temperature coefficient, so more output on a hot roof.
- +Lower degradation and often a 30-year power warranty.
- +N-type base, so no boron-oxygen light-induced degradation.
- +Higher bifacial gain for ground mounts and reflective surfaces.
The verdict
For a new system in 2026, buy TOPCon where it is available, which by now is most of the market. It is a little more efficient, holds output better in heat, degrades more slowly, and often carries a longer warranty, all for little or no price premium over PERC. That said, the gap is modest, so do not overpay chasing the label. A well-priced PERC panel from a reputable brand with a strong warranty is still a good panel, and the install quality, warranty, and price per watt matter more to your results than PERC versus TOPCon. Match the array to your usage with the solar panel calculator and compare real models before you decide.
Related: Best solar panels, What is a solar cell?, Solar panel calculator.
Frequently asked questions
Is TOPCon better than PERC?
Yes, modestly. TOPCon modules run about 22 to 23% efficient versus 20 to 21.5% for PERC, degrade more slowly (about 1% in year one versus 2%), hold output better in heat, and often carry a 30-year warranty instead of 25. The margin on an average rooftop is a few percent of annual production, so it is a real but small edge, not a night-and-day difference.
What is a TOPCon solar panel?
A TOPCon solar panel uses N-type silicon cells with a Tunnel Oxide Passivated Contact: an ultra-thin oxide layer and a doped polysilicon layer on the rear that cut the electrical losses found in older PERC cells. The result is higher efficiency, better heat performance, and slower degradation. As of 2025 TOPCon became the leading technology in new panel production.
Should I pay more for TOPCon over PERC?
Usually you do not have to. Because TOPCon is now the market default, it often costs the same or less than PERC, which is being phased out. If a TOPCon panel carries only a small premium, it is worth it for the better efficiency, heat performance, and warranty. If the premium is large, a well-priced PERC panel from a solid brand is a fine choice.
What is the difference between PERC and TOPCon?
PERC uses a P-type silicon base with a passivation layer and reflector on the rear. TOPCon uses an N-type base plus a thin tunnel oxide and a doped polysilicon contact that reduces recombination losses. Both are monocrystalline, but TOPCon's design gives it higher efficiency, a better temperature coefficient, lower degradation, and higher bifacial gain.
Which solar cell type is the most efficient?
Among panels you can buy, back-contact (IBC) and heterojunction (HJT) cells lead, reaching about 22.5 to 26% in production, followed by TOPCon at about 22 to 23%, then PERC at about 20 to 21.5%. In the lab, perovskite-on-silicon tandem cells have passed 34%, but they are not yet sold for home use. See the solar panel efficiency guide for the full breakdown.
Is PERC being discontinued?
It is being phased out, not banned. Manufacturers have converted most new cell capacity to TOPCon since 2024, so PERC is increasingly the clearance and budget tier rather than the default. You can still buy PERC panels, and they work well; there are just fewer new models, and the price advantage that once justified them has largely gone.