What is polycrystalline
Polycrystalline solar, also called multi-crystalline silicon (mc-Si), refers to PV modules whose cells are cut from silicon wafers cast from molten silicon that solidifies as multiple grains. The wafers contain many small crystals separated by grain boundaries. Cells are processed through diffusion, metallisation and interconnection similar to monocrystalline.
For two decades polycrystalline was the cost-effective workhorse of global solar deployment. Lower manufacturing energy, simpler casting process and easier ingot growth gave poly a structural cost advantage. From roughly 2020 onward, monocrystalline manufacturing scaled to a point where mono cost per watt fell below poly, eliminating poly’s commercial advantage. By 2026, poly is a legacy technology with limited new deployment.
In India, polycrystalline dominated rooftop and utility solar from 2010 to 2020. Tata Power Solar, Vikram Solar, Waaree and several others sold gigawatts of poly modules during this period. From 2022 onward, ALMM listings shifted heavily toward mono, and most new Indian installations specify mono.
Polycrystalline explained simply
Think of mono silicon as a single ice crystal grown slowly under controlled conditions, and poly silicon as ice cubes frozen quickly into a tray with many grains. The poly version is faster and cheaper to make but the grain boundaries inside reduce efficiency. A poly cell converts about 17 to 19 percent of sunlight to electricity, against 20 to 23 percent for modern mono, a gap captured directly in module efficiency ratings. Most Indian buyers now know to ask whether a quote is mono or poly; see common solar inverter buying mistakes for why the same scrutiny needs to extend to the solar inverter, not just the panel.
Why polycrystalline still matters
Legacy installation base. Hundreds of GW of installed poly worldwide, including roughly 30 GW in India.
Replacement supply. Existing poly arrays need spare modules with matching electrical characteristics.
Specific budget markets. Some cost-sensitive small applications still source poly.
Historical context. Understanding poly informs the choice for new installations.
How polycrystalline works
- Molten silicon poured into a casting mould.
- Slow cooling creates many small crystal grains.
- Ingot sliced into wafers.
- Wafers processed through doping, anti-reflective coating, metallisation.
- Cells interconnected with ribbons or busbars.
- Encapsulated between glass and back sheet.
The fundamental physics is identical to monocrystalline. The difference is the silicon’s crystal structure: many small grains in poly, one large grain in mono. Grain boundaries trap electrons and reduce open-circuit voltage.
Technical deep dive
Cell efficiency progression
| Year | Standard poly cell |
|---|---|
| 2010 | 15.5% |
| 2015 | 17.5% |
| 2018 | 18.5% |
| 2020 | 19.5% (PERC poly) |
| 2022 | 20.0% (PERC poly, plateau) |
PERC technology added efficiency to poly but the gap to mono never closed.
Module efficiency
| Year | Standard poly module |
|---|---|
| 2010 | 13 to 14% |
| 2015 | 15 to 16% |
| 2020 | 17 to 18% |
| 2025 | 17 to 19% |
Temperature coefficient
| Parameter | Poly | Mono PERC |
|---|---|---|
| Voc coefficient (%/°C) | -0.30 to -0.32 | -0.27 to -0.30 |
| Pmax coefficient (%/°C) | -0.39 to -0.41 | -0.34 to -0.37 |
Poly is slightly worse at high temperatures, which matters in Indian summers.
Degradation
| Mechanism | Poly |
|---|---|
| LID first month | 1 to 2.5% |
| Annual degradation | 0.6 to 0.8%/year |
| 25-year retention | 80 to 83% |
Real-world applications
Legacy rooftop systems installed 2010 to 2020.
Spare module supply for existing poly arrays.
Budget off-grid systems in some markets.
Educational and demonstration installations.
Advantages of polycrystalline
Lower upfront cost (historically).
Wide manufacturing footprint built up over two decades.
Lower manufacturing carbon footprint than early mono.
Familiar to installers.
Compatible with same balance-of-system components as mono.
Limitations
Lower efficiency. Less power per square metre.
Slower technology progression. No clear path to TOPCon or HJT-like jumps.
Slightly higher temperature coefficient.
Slightly worse degradation profile.
ALMM listings increasingly dominated by mono.
Bifacial module development limited.
For a cost breakdown that puts budget polycrystalline modules side by side with mid-range PERC and premium TOPCon panels, see 10kW solar system price in India.
Common problems
PID susceptibility. Older poly modules without PID-resistant materials suffer significant degradation in 5 to 10 years.
Snail trails and back sheet issues similar to mono.
Hot spots from cracked cells.
Limited replacement availability for older specific wattages.
String mismatch when mixing replacement modules with original array.
Soiling losses similar to mono, 5 to 25 percent depending on cleaning schedule.
Best practices
Verify ALMM listing and BIS certification.
Match replacement modules to original Voc, Imp and Vmp specifications.
Use PID-resistant modules in systems with grounded inverter.
Document module serial numbers and electrical parameters.
Plan annual cleaning.
Comparison: poly vs mono PERC vs mono TOPCon
| Feature | Polycrystalline | Mono PERC | Mono TOPCon |
|---|---|---|---|
| Module efficiency | 17 to 19% | 20 to 22% | 22 to 23.5% |
| Annual degradation | 0.6 to 0.8% | 0.45 to 0.55% | 0.40 to 0.50% |
| Temperature coefficient | -0.40%/°C | -0.36%/°C | -0.31%/°C |
| Price per watt (₹) | 15 to 22 | 16 to 24 | 18 to 26 |
| Roof area for 5 kW | ~35 m² | ~30 m² | ~26 m² |
| ALMM availability | Limited | Wide | Wide |
Indian market context
Polycrystalline dominated Indian solar from 2010 to 2020 through the National Solar Mission (Phase I, II, III).
ALMM List I now contains predominantly mono modules. Poly listings are limited and shrinking.
Most Indian module manufacturers (Waaree, Adani Green Solar, Tata Power Solar, Vikram Solar, Goldi Solar, Premier Energies) have shifted production capacity to mono PERC and TOPCon.
PM Surya Ghar accepts ALMM-listed poly modules, but supply availability is limited. Most installers default to mono.
Legacy poly systems installed before 2020 continue to operate. Operations and maintenance for these systems remains an active business.
Standards and certifications
| Standard | Scope |
|---|---|
| IEC 61215 | Crystalline silicon module qualification (covers both mono and poly) |
| IEC 61730-1, -2 | Module safety qualification |
| IEC 62804 | PID test |
| IS 14286 | Indian Standard for crystalline silicon modules |
| MNRE ALMM | Listing for subsidies |
| BIS certification | Quality compliance |
Common mistakes
Buying poly to save money. Mono price gap has closed; no significant saving available.
Mixing mono and poly in one string. 5 to 15 percent string mismatch loss.
Trusting older poly modules without PID test certification.
Ignoring temperature coefficient in tropical Indian conditions.
Choosing poly for ALMM-eligible projects when better mono alternatives are listed.
Key takeaways
Polycrystalline is a legacy crystalline silicon technology that dominated the early decade of solar PV. Modern manufacturing scale has shifted the cost advantage to mono. Poly continues to serve legacy installations and replacement supply but has lost the new-deployment market. For any new Indian solar project, mono is the obvious choice.
Need legacy poly module replacement?
Qbits Energy makes solar inverters and does not supply solar modules. For a replacement poly module where mono substitution is not feasible due to mismatch, match the original Voc, Imp and Vmp as described above and source it through your installer or a module distributor. If the legacy array feeds a Qbits inverter, check the replacement module’s Voc and Imp against that inverter’s datasheet input window.
Further reading
For how Polycrystalline plays out in real projects, these guides go deeper:
- Solar Panel ki Kimat 2026: Poora Rate Guide
- Solar Subsidy Form: How to Download & Fill It
- Best Solar System Under ₹1 Lakh in India 2026
- Solar Panel Price in India 2026: All Brands, All Wattages
Sources
- IEC 61215, Terrestrial photovoltaic modules: Design qualification.
- IEC 61730-1, -2, Module safety.
- IEC 62804, PID test.
- IS 14286, Indian Standard for crystalline silicon PV modules.
- MNRE Approved List of Models and Manufacturers (ALMM), List I.
- NREL Best Research-Cell Efficiency Chart.
- ITRPV Roadmap, latest edition, VDMA.
- IEA PVPS Trends in Photovoltaic Applications 2024.
- Manufacturer technical datasheets from Indian module manufacturers.
Frequently Asked Questions
What is a polycrystalline panel in simple words?
Polycrystalline vs monocrystalline?
What is the efficiency of poly panels?
Are poly panels still made?
Are poly panels cheaper?
How do you tell mono and poly apart visually?
Are poly panels ALMM-listed?
Do poly panels degrade faster?
What is the temperature coefficient of poly?
How long do poly panels last?
Can I mix poly and mono in one string?
Are poly modules bifacial?
Do poly modules have LID?
Are poly cells thicker than mono?
Why has poly declined?
From the Blog
Co-founder & CEO driving Qbits Energy's product strategy and growth across India.