Quick answer
PERC Solar Panel A PERC solar panel is a panel built from passivated emitter and rear cells: standard p-type silicon cells with an extra insulating layer on the back that bounces unused light back through the cell and stops electrons being lost at the rear surface.
PERC was the mainstream cell for most of the last decade. In 2024 n-type TOPCon overtook it in market share, and roadmap figures put PERC modules about two points of efficiency behind.
Quick facts
The key facts about perc solar panel, with sources:
- Stands for
- Passivated Emitter and Rear Cell (also "rear contact")
- Wafer
- p-type monocrystalline silicon 2
- What changed from older cells
- A dielectric (insulating) rear layer with local contacts replaced a full aluminium back 23
- Typical module efficiency (2025)
- 21.7% PERC vs 23.5% TOPCon, ITRPV survey 1
- Example temp. coefficient
- −0.34%/°C (Canadian Solar HiKu6 mono PERC) 6
- Market position
- Overtaken by TOPCon in 2024 1
Key takeaways
- PERC adds an insulating layer to the back of a normal silicon cell. It reflects light for a second pass and cuts electron losses.
- It was the main cell type for about a decade. TOPCon overtook it in 2024.
- PERC panels average about 21.7% efficiency, against 23.5% for TOPCon, in the 2025 ITRPV survey.
- A PERC panel is not a bad panel. Compare its heat loss, yearly wear and warranty against a current n-type quote.
- Ask about replacement-part support, since fewer new PERC models are being made.
What PERC means in plain words
Each word in the name points to part of the cell. The emitter is the thin top layer of the cell where current is gathered. Passivated means a surface is coated so it stops wasting electrons, the tiny charges that sunlight frees. Rear is the back of the cell.
So a PERC cell is one whose front and back surfaces are both coated to cut losses. Fraunhofer ISE researchers put it simply: compared with a standard cell with an aluminium back, a PERC cell has a "dielectrically passivated rear surface with local contacts", while the front is typically the same.
Dielectric means electrically insulating. The cell sits on a p-type monocrystalline silicon wafer, the kind most panels used before n-type wafers took over.
Sources: [2]
What the "passivated rear" adds
An older silicon cell had a solid aluminium layer across its back, called an aluminium back surface field (Al-BSF). PERC changes three things there 2 3.
- A thin insulating film is laid on the back of the wafer. Researchers often use aluminium oxide at least 10 nm thick, capped with silicon nitride 3. The film cuts the loss of freed electrons at the rear surface, which lets the cell hold a higher voltage 2.
- The same film works as a mirror. Some red and infrared light crosses the cell without being absorbed. The rear film reflects more of it back inside than an aluminium back does, which lengthens the light’s path through the silicon 3.
- A laser opens small spots in the film so the rear metal can still touch the silicon. Fraunhofer ISE describes these as laser fired contacts, made after the metal is printed 2.
More light caught and fewer electrons lost add up to more power from the same wafer. That gain is why PERC replaced the older full-aluminium cell 3.
Types of PERC products on real data sheets
| Product | Cell type line | Efficiency | Temp. coefficient |
|---|---|---|---|
| Canadian Solar HiKu6 CS6R-MS (2022) 6 | "Mono PERC" in the product name | 20.2%–21.5% | −0.34%/°C |
| GAF Energy Timberline Solar energy shingle SM210 (2021) 8 | "Monocrystalline PERC" | Not stated; 45 W per shingle | −0.39%/°C |
PERC variants you may see named
Mono PERC is the standard home panel version: PERC cells on single-crystal wafers.
Bifacial PERC uses a rear film with open contact lines, so light can enter from the back too. ITRPV expects PERC bifaciality to top out near 73%, lower than TOPCon or heterojunction. See bifacial panels.
MWT-PERC (metal wrap through) moves the main contacts to the back to cut front shading. Fraunhofer ISE tested it alongside standard PERC in 2013.
Example: PERC vs TOPCon from one maker on a hot day
Both panels are from Canadian Solar data sheets. The 40 °C rise above 25 °C is our assumption for hot cells on a summer roof, not a measured value.
| Line | HiKu6 mono PERC 6 | TOPHiKu6 TOPCon 7 |
|---|---|---|
| Max module efficiency | 21.5% | 23.4% |
| Watts per m² at 1,000 W/m² light | 215 W | 234 W |
| Temp. coefficient (Pmax) | −0.34%/°C | −0.29%/°C |
| Loss if cells run 40 °C hotter | 40 × 0.34% = 13.6% | 40 × 0.29% = 11.6% |
| Watts per m² at that heat (our math) | 215 × 0.864 ≈ 186 W | 234 × 0.884 ≈ 207 W |
In this simple math the TOPCon panel makes about 11% more per square metre on a hot day. On a large roof, a cheaper PERC system with a few more panels can still make the same yearly kWh.
Where you will still find PERC
On millions of existing roofs. PERC was the mainstream cell for most of the last decade, so many systems built in that time use it.
On some current quotes, too. The DOE notes the industry is shifting from PERC toward n-type cells like TOPCon and heterojunction. ITRPV’s 2025 silver estimate still assumes a 15% PERC share.
In some specialty products. GAF’s 2021 Timberline Solar shingle data sheet lists monocrystalline PERC cells; see solar shingles.
Benefits and limits of PERC panels
Benefits
- Clear gain over older aluminium-back cells, from rear passivation and reflection 3.
- Mature and well proven after a decade of mass production.
- Often sold as older stock, which can lower the price per watt.
- Works with all common inverters and racking.
Why the industry moved on
PERC squeezed most of what it could from p-type wafers. The ITRPV 17th Edition reports that n-type wafers took about 82% of the market in 2025, driven by the fast switch to TOPCon. TOPCon’s passivated contacts reach higher voltages. The roadmap expects PERC to keep phasing out.
That does not make a PERC panel a bad panel. It means fewer new models, and more PERC stock sold as older product.
What drives the cost of a PERC system
HyreSolar does not publish panel prices. A PERC quote can be cheaper per watt because the product is older. The installed price still depends mostly on system size, roof work, permits and labor. Compare on cost per watt and on yearly kWh.
Lifespan sets value. DOE cites a Berkeley Lab finding that average panel life reached 25–35 years in 2025. Read the warranty’s yearly loss figure; our degradation guide shows how it adds up.
The federal 25D homeowner credit ended for systems placed in service after 31 December 2025, the IRS says.
How PERC panels are installed
The steps match any silicon panel. A licensed installer and electrician do the work.
- The installer checks your roof, shade and past year of power use.
- They size the system and give you the panel data sheet and a yearly kWh estimate.
- They confirm panel voltage and current fit the inverter input.
- They apply for permits and for utility interconnection.
- Crews install racking, panels and wiring. An inspector checks the work.
- The utility grants permission to operate.
Caring for PERC panels
Care is the same as for any silicon panel. Watch monitoring, compare each month with last year, and keep heavy dirt off the glass. Our cleaning guide covers safe methods.
Expect a slow decline. An NREL review of nearly 2,000 measured rates found a median loss of 0.5% a year across panels. Your warranty sets the rate you can claim against.
Sources: [5]
Warning signs and when to call a pro
Call a licensed installer or electrician for any of these. Do not touch panels or wiring.
- Output falls faster than the warranty’s yearly rate.
- A panel or string reads far below the others.
- Cracks, burn marks or bubbles on the glass.
- Inverter error codes that keep returning.
Safety rule
Panels make voltage whenever light hits them. Only a licensed pro should work on any part of the system.
Standards and rules that apply
Product listing. UL says the NEC, IBC and IRC require PV products on or near buildings to be certified by a Nationally Recognized Testing Laboratory. The panel safety standard is UL 61730-1 and -2, harmonized with IEC 61730. No code treats PERC differently from other cells.
Local codes. Your city or county enforces the code editions it has adopted. In South Carolina, the SC Building Codes Council lists the 2021 codes as in force.
Solar roofing. PERC shingles that serve as the roof covering are building-integrated PV. UL says the 2021 IBC and IRC require BIPV roofing to be listed to UL 7103.
PERC vs the n-type cells that replaced it
| PERC | TOPCon | Heterojunction | |
|---|---|---|---|
| Wafer type | p-type | n-type | n-type |
| Module efficiency, ITRPV 2025 | 21.7% | 23.5% | 23.5% |
| Bifaciality factor outlook | Up to 73% | Up to 85% | Above 90% |
| Share assumed in ITRPV’s 2025 silver estimate | 15% | 75% | 5% |
Sources: [1]
Misconceptions
- Myth PERC panels are obsolete and should be avoided.
- Reality They are older, not faulty. A well-priced PERC system can make the same yearly kWh with a few more panels.
- Myth PERC is a type of panel, separate from mono.
- Reality PERC is a cell design. Home PERC panels are built on monocrystalline wafers, hence "mono PERC".
- Myth The rear layer is just a coating for looks.
- Reality It cuts electron loss and reflects light back into the cell 3.
PERC panels in SC, GA and VA
Hot, humid summers across SC, GA and VA make the temperature coefficient worth comparing on any PERC quote. State rules do not pick cell types. South Carolina customers who applied after 1 June 2021 use a Solar Choice tariff under Act 62 13.
Georgia Power caps residential renewable systems at 10 kW, so higher-efficiency panels fit more output within that cap only when roof space is short 14. Virginia allows residential net metering up to 25 kW on investor-owned utilities 15.
If your quote lists PERC panels
- Check the data sheet date and whether the model is current. Ask what replacement-part support looks like.
- Compare the temperature coefficient and the warranted yearly loss.
- Ask for the same system priced with a current n-type panel. If PERC is clearly cheaper per watt, it may still be the better buy.
- Confirm the panel fits your inverter plan; voltage and current must suit the inverter input.
Next steps
- Solar proposal analyzerCheck the panel and price lines on a quote
- Solar panel efficiencyData-sheet numbers explained
Questions about perc solar panel
Is PERC better than TOPCon?
No. On the ITRPV 2025 survey TOPCon panels average 23.5% efficiency against 21.7% for PERC. Current TOPCon data sheets also show lower temperature coefficients. PERC can still be a sound choice if the price per watt is clearly lower and your roof has room.
Are PERC panels being discontinued?
They are being phased out. TOPCon passed PERC in market share in 2024, and the ITRPV roadmap expects PERC production to keep shrinking. The DOE also describes an industry shift to n-type cells. Existing PERC panels keep working and stay under their warranties.
Is PERC monocrystalline?
Almost always. Home PERC panels use p-type monocrystalline wafers, which is why data sheets often say mono PERC. Fraunhofer ISE’s PERC research focused on monocrystalline p-type cells. A few older poly PERC panels exist too.
What does PERC stand for?
Passivated Emitter and Rear Cell, sometimes written Passivated Emitter and Rear Contact. Both names describe the insulating layer added to the back of the cell. Passivated means coated to stop electrons being lost at the surface.
How does a PERC cell make more power?
Its rear film does two jobs. It cuts the loss of electrons at the back surface, which raises the voltage. It also reflects unabsorbed red and infrared light back into the silicon for a second pass. Together these beat the older aluminium-back cell.
How long do PERC panels last?
Like other silicon panels, often 25 to 35 years. DOE cites a Berkeley Lab finding that average panel life reached 25–35 years in 2025. An NREL review found a median output loss of 0.5% a year across panels. Your warranty sets the yearly loss you can claim against.
Do PERC panels lose more power in the heat?
A little more than current n-type panels. The HiKu6 PERC sheet lists −0.34% per degree, while the TOPHiKu6 TOPCon sheet lists −0.29%. On a hot roof that gap can mean a few percent less output at midday.
Should I buy PERC panels in 2026?
Only if the price is right. Ask for the same system with a current n-type panel. If PERC is clearly cheaper per watt and your roof has space, it can still make sense. Check the data sheet date, warranty and replacement-part support first.
Can PERC panels be bifacial?
Yes. Bifacial PERC leaves openings in the rear film and uses a clear back so light enters from behind. ITRPV expects PERC bifaciality to peak near 73%, below TOPCon and heterojunction.
Sources
- VDMA, International Technology Roadmap for Photovoltaic (ITRPV), 17th Edition, Results 2025 (June 2026), retrieved .
- Mack et al., Fraunhofer ISE, Technologies for Mass Production of >20% Efficient p-Type Silicon Solar Cells (28th EU PVSEC, 2013), retrieved .
- Davis et al., Investigation of the Internal Back Reflectance of Rear-Side Dielectric Stacks for c-Si Solar Cells, IEEE Journal of Photovoltaics (author copy, UCF CREOL), retrieved .
- US DOE Solar Energy Technologies Office, Crystalline Silicon Photovoltaics Research, retrieved .
- Jordan and Kurtz, NREL, Photovoltaic Degradation Rates — An Analytical Review (NREL/JA-5200-51664, 2012), retrieved .
- Canadian Solar, HiKu6 Mono PERC CS6R-MS data sheet V1.7C25_AU (April 2022), retrieved .
- Canadian Solar, TOPHiKu6 CS6.2-54TM data sheet V1.2_EN (March 2025), retrieved .
- GAF Energy, Timberline Solar technical data sheet #837 SM210 (December 2021), retrieved .
- US DOE Solar Energy Technologies Office, End-of-Life Management for Solar Photovoltaics, retrieved .
- UL Solutions, Building-Integrated Photovoltaic (BIPV) System Testing and Certification (UL 7103, UL 61730), retrieved .
- IRS, Residential Clean Energy Credit (§25D), retrieved .
- SC Building Codes Council, code adoption, retrieved .
- South Carolina Code Title 58 Ch. 40 (Act 62 of 2019, customer-generators), retrieved .
- Georgia Power, Behind-the-Meter Interconnection Summary for Residential Customers (rev. 15 Aug 2025), retrieved .
- Code of Virginia §56-594 (net energy metering), retrieved .
Expert review
Written by the HyreSolar Research team. Not yet reviewed by an outside expert. We say so rather than imply a review that has not happened; see our editorial policy.
How the numbers were checked: Cell physics is cited to Fraunhofer ISE (Mack et al., 2013: dielectric rear passivation, local and laser fired contacts, higher voltage) and Davis et al., IEEE Journal of Photovoltaics (rear-surface recombination, internal back reflectance vs Al-BSF, AlOx thickness).
Efficiency, share and bifaciality figures from ITRPV 17th Edition (the 15:75:5:5 split is the assumption the roadmap uses for its 2025 silver estimate). Product specs read from the named data sheets; the hot-day example uses an assumed 40 °C rise.
Suggest a correction. We fix errors and say what changed.