Are Polycrystalline Solar Panels Worth It Pros, Cons and 2025 Buying Tips
Polycrystalline panels deliver 18-20% efficiency, cost $0.18-0.22/W—affordable but space - hungry. 2025 tip: Choose anti - PID models with low - iron glass, install at 30° tilt; worth it for budget - conscious small - scale projects.
Advantages and Disadvantages
Globally, 70% of modules are polycrystalline, and in China, nine out of ten home installations choose it. But in the last five years, monocrystalline silicon has staged a comeback with PERC and TOPCon technologies. In 2023, the market share of monocrystalline modules soared to 95%, leaving polycrystalline with less than 5%. It's not that polycrystalline has gotten worse; it's that monocrystalline efficiency has increased too fast: mainstream polycrystalline efficiency is stuck at 18%-20%, while monocrystalline PERC reaches 22%-23%, and TOPCon is approaching 25%.
Advantages
Out of the global 104GW PV installations, 73GW used polycrystalline modules, accounting for 70%. Back then, installing a 10kW home system, polycrystalline was 20,000 yuan cheaper than monocrystalline. Farmers in Henan and Shandong calculated: polycrystalline had a faster payback, recouping the cost in 5 years, while monocrystalline took 6-7 years. But in recent years, monocrystalline has captured the market with technology; by 2023, polycrystalline's share dropped to less than 5%.
Casting Method Saves Costs, Silicon Wafers are Over 15% Cheaper
Monocrystalline requires the Czochralski method, pulling silicon material into a single-crystal rod like pulling candy hawthorns, requiring temperatures above 1450°C, consuming more electricity and taking longer. Let the data speak: producing 1kg of silicon ingot by casting consumes 18-22 kWh of electricity, while the Czochralski method requires 40-45 kWh, saving over half the electricity per kilogram. Reflected in wafer cost, in 2023, polycrystalline wafers cost 0.8 yuan/piece, monocrystalline 1.0-1.1 yuan/piece, the silicon wafer cost per watt for modules is lower by 0.15-0.2 yuan. Adding similar usage of packaging materials (glass, encapsulant), the final factory price for polycrystalline modules is 1.3 yuan/W, monocrystalline 1.55 yuan/W. For a 10kW system, polycrystalline directly saves 25,000 yuan. A PV distributor in Yunnan said: "Rural users value this the most. For the same 10kW, polycrystalline installed price is 120,000 yuan, monocrystalline 145,000 yuan.
20 Years of Process Maturity, Degradation Stabilized for Reliable Calculation
Polycrystalline technology has been around since the 1980s; mass production in China started in the early 2000s. Now there are over 200 supporting factories nationwide (ingot pulling, slicing, packaging). Data from third-party testing agency TÜV: polycrystalline modules have first-year degradation of 2% (industry standard ≤2.5%), thereafter 0.45%-0.55% annually, total degradation over 25 years is 18%-20%, just guaranteeing 80% power. A polycrystalline power station installed in Jiangsu in 2015 measured power after 8 years of operation: initial 30kW, now still 24.2kW, average annual degradation 0.7%, slightly higher than the manufacturer's promised 0.5%, but not much different from some monocrystalline new technologies installed at the same time (average 0.65%). More substantially, this stable degradation allows accurate profit calculation – installing 10kW polycrystalline, total generation over 25 years is about 380,000 kWh (based on 15,000 kWh/year). If degradation were faster, it might generate 50,000 kWh less, directly losing 25,000 yuan (at 0.5 yuan/kWh electricity price).
Can Generate More on Cloudy Days, Earning an Extra Two to Three Thousand per Year
At irradiance of 500W/㎡ (equivalent to a cloudy morning at 10 AM), polycrystalline conversion efficiency is 3%-5% higher than monocrystalline. Measured data from an agricultural-photovoltaic complementary project in Shandong: 30% of the year is cloudy or overcast. Polycrystalline annual generation: 12,500 kWh, monocrystalline: 12,000 kWh. A 10kW system generates 500 kWh more per year, 5,000 kWh more over 10 years. At 0.4 yuan/kWh (surplus electricity feed-in tariff), it earns an extra 2,000 yuan. It's more pronounced in Guizhou – average annual sunshine hours 1100, cloudy days account for 40%. Polycrystalline annual generation: 11,000 kWh, monocrystalline: 10,500 kWh. Difference over 10 years: 5,000 kWh, earning an extra 2,500 yuan.
Can Be Remelted After Decommissioning, Silicon Material Recycling Saves 40% Cost
Silicon wafers account for 40% of module cost, glass 20%, aluminum frame 10%. Recycling technology is now mature: using acid etching to separate silicon wafers, purity can reach 99.99% (electronic-grade silicon material standard is 99.9999%, but it's sufficient for ingot casting). Data from Germany's Fraunhofer Institute: 1 ton of polycrystalline modules can yield 850kg of silicon material, 120kg of glass, 80kg of aluminum. Reselling the silicon material can recover 3,000 yuan (new silicon material price is about 18,000 yuan/ton). A domestic recycling plant calculated: total revenue from recycling 1 ton of polycrystalline modules is about 4,500 yuan, cost 3,000 yuan, net profit 1,500 yuan, more cost-effective than processing monocrystalline modules (silicon material purification is more difficult, net profit 800 yuan). Some power stations in Zhejiang have already signed recycling agreements; decommissioning after 25 years can recover 30% of the module's residual value, equivalent to earning a "pension" for free.
Small Batch Purchases Aren't Expensive, Suitable for Scattered Installations
Due to high demand, monocrystalline manufacturers prefer large orders; small batches (e.g., below 100kW) have a 5%-8% premium. Polycrystalline is the opposite – there are many small and medium-sized factories, flexibly accepting small orders. A installation company in Shandong compared: ordering 100kW monocrystalline, unit price 1.6 yuan/W; polycrystalline 1.4 yuan/W. The difference for 100kW is 20,000 yuan. This is friendly to rural cooperatives, township enterprises – they can get low prices without pooling resources for large projects. A village collective in Hebei installed a 50kW system, chose polycrystalline and saved 10,000 yuan, just enough to add monitoring equipment, "spending money where it matters."
Shortcomings
In 2023, a farmer in Zhejiang installed a 10kW polycrystalline system. First-year generation: 11,000 kWh. The neighbor's monocrystalline system generated 12,500 kWh – earning 750 yuan less per year. This gap widens over time: by year 10, cumulative polycrystalline generation: 108,000 kWh, monocrystalline: 128,000 kWh. Difference 20,000 kWh, losing 10,000 yuan.
On hot summer days, polycrystalline power drops 20% at 2 PM, monocrystalline only 15%. After 5 years, wanting to replace panels, the distributor said "polycrystalline parts have long been discontinued."
Lower Efficiency, Losing Enough for a Car Over 10 Years
Mainstream polycrystalline efficiency is stuck at 18%-20% (2023 data), monocrystalline PERC reaches 22%-23%, TOPCon approaches 25%. Don't underestimate this 3%-5% gap. For a 10kW system, it generates 500-1,000 kWh less per year. In Yunnan, with good irradiance (1800 annual sunshine hours), polycrystalline generates 16,000 kWh/year, monocrystalline 17,500 kWh/year. Difference over 10 years: 15,000 kWh, losing 7,500 yuan (at 0.5 yuan/kWh). It's worse in Sichuan – average annual sunshine 1200 hours, polycrystalline 11,000 kWh/year, monocrystalline 12,000 kWh/year. Difference over 10 years: 10,000 kWh, losing 5,000 yuan. Monocrystalline is still improving; TOPCon efficiency increases 0.5% annually, while polycrystalline has long been stagnant at 19%. In 5 years, the gap will widen to 15%, equivalent to throwing away half a panel's cost.
Power Drops Faster on Hot Days, Summer Revenue Discounted by 30%
Polycrystalline temperature coefficient is -0.45%/°C (monocrystalline -0.35%/°C), meaning power decreases by 0.45% for every 1°C temperature increase. In summer, panel surface temperature can reach 70°C (ambient 35°C). Polycrystalline power directly drops by (70-25) × 0.45% = 20.25%, monocrystalline only 15.75%. Measured data from a power station in Xinjiang: from noon to 3 PM in July, polycrystalline generated 12 kWh/hour, monocrystalline 14.5 kWh/hour. 3 hours less generation: 7.5 kWh, per month 225 kWh less, per year 2,700 kWh less. At 0.4 yuan/kWh (surplus feed-in), losing 1,080 yuan. Worse, high temperatures also accelerate module aging – polycrystalline operating at 70°C has 0.05% higher annual degradation than monocrystalline. Over 25 years, degradation is 1.25% more, equivalent to generating 1,500 kWh less.
Poor Appearance, Secretly Reduces Second-hand House Valuation by 20%
A survey by a PV installation company of 500 houses with PV: 80% of high-end community owners chose monocrystalline, reasoning "polycrystalline looks like industrial waste." Data from a real estate platform is more direct: for similar units in the same location, second-hand quotes for houses with polycrystalline roofs are 15%-20% lower than those with monocrystalline. A house in Jiangsu was appraised at 3 million yuan before installing polycrystalline; after installation, the offer was cut to 2.55 million, directly losing 450,000 yuan.
Uncertain After-sales, Searching for Parts for Half a Year if Broken
In 2023, polycrystalline module production capacity share dropped to 8% (was 70% in 2015). Major manufacturers like LONGi, Jinko stopped polycrystalline production lines long ago. A distributor said: "Ordering polycrystalline parts now requires finding small factories that refurbish old materials." Last year, a client in Shandong needed to replace a micro-cracked polycrystalline panel. Contacted 3 suppliers, waited 2 months to receive the goods. During this time, the power station generated 200 kWh less. Even more critical, after 2025, mainstream encapsulant film (EVA) manufacturers may stop producing polycrystalline-specific versions. Then, if a panel cracks, there's nowhere to buy the adhesive. Statistics from an O&M company: average repair time for polycrystalline station faults is 7 days, monocrystalline only 2 days. The extra 5 days are enough to lose 150 kWh.
Small Batch Purchases are Expensive, Scattered Installation is Even Less Cost-Effective
Due to high demand, monocrystalline manufacturers love large orders; small orders below 100kW have a 5%-8% premium. Although polycrystalline is flexible, small factories have poor technology and low yield – for 100kW of polycrystalline panels, the defect rate is 2% higher than monocrystalline, equivalent to spending an extra 2,000 yuan on defective products. A cooperative in Hebei installed 30kW polycrystalline. Measured generation was 8% less than expected. Investigation found 3 panels with micro-cracks. Loss of 2,400 kWh, enough to pay half a year's property fee. Worse, these defective panels are out of warranty (5 years), the manufacturer doesn't repair them, they have to pay for replacement themselves. Cost per panel 300 yuan, 3 panels 900 yuan.
Trends and Purchasing Advice
In the global PV market of 2023, the share of polycrystalline modules had fallen to 18% (PV InfoLink data), a significant shrinkage from 45% in 2019. By 2025, polysilicon prices are expected to stabilize at 60-70 yuan/kg (was about 80 yuan/kg in 2023). Coupled with a further 10%-15% reduction in non-silicon costs after technical upgrades to poly production lines (from 0.3 yuan/W to 0.25-0.27 yuan/W), its "low-price advantage" becomes prominent again in specific scenarios.
For example, a rural user in Henan installed an 8kW polycrystalline rooftop system. The initial cost was 6,400 yuan lower than monocrystalline (based on a 0.8 yuan/W price difference). If annual generation is 10,000 kWh, the payback period is only 5.8 years (monocrystalline requires 5.2 years), a difference of 0.6 years, but the total profit difference is less than 2,000 yuan.
3 Major Trends
Global PV installations surged to 495GW in 2023 (IEA data), but polycrystalline modules only got an 18% slice of the pie – this figure was 45% in 2019. Why? Monocrystalline PERC, TOPCon and other new technologies are too strong, with efficiency jumping from 22% to 25%, making poly's 18%-19% look inadequate.
But polycrystalline won't disappear completely in 2025: polysilicon prices are expected to drop to 60-70 yuan/kg (was 80 yuan/kg in 2023), and poly non-silicon costs will drop another 10%-15% (from 0.3 yuan/W to 0.25-0.27 yuan/W), making it 0.1-0.15 yuan/W cheaper (saving 5,000-7,500 yuan for a 50kW system). A rural user in Zhoukou, Henan, installed 8kW of polycrystalline in 2024, spending 6,400 yuan less than monocrystalline. Annual generation 10,000 kWh, payback period 5.8 years (monocrystalline 5.2 years) – a difference of 0.6 years, but the total profit over 25 years is only 1,800 yuan less.
Market Shrinks, But Becomes More Popular in Low-Irradiance Regions
PV InfoLink data shows the global polycrystalline market share was 45% in 2019, dropped to 18% in 2023, and is projected to be only 15%-17% in 2025. But don't panic, it specifically targets "tough nuts" – regions with annual irradiance < 1400 hours (like Sichuan, Guizhou, Chongqing). In these areas, monocrystalline's high-efficiency advantage is weakened: for the same 50kW installation, monocrystalline annual generation is 65,000 kWh, polycrystalline 62,000 kWh, the gap shrinks to within 5% (used to be 8%-10%). Cost: polycrystalline is 0.12 yuan/W cheaper than monocrystalline, total system cost for 50kW is 6,000 yuan lower. The generation profit can cover this cost difference in 3 years.
A commercial & industrial user in Panzhihua, Sichuan, installed PV on a 1000㎡ factory roof in 2024, choosing polycrystalline. He calculated: local annual irradiance 1250 hours, monocrystalline annual generation 1.15 million kWh, polycrystalline 1.10 million kWh, earning 23,000 yuan less (selling electricity at 0.4 yuan/kWh). But the initial cost of polycrystalline was 120,000 yuan lower (1000㎡ × 120W/㎡ × 0.12 yuan/W), payback in 5 years, then pure profit for the next 20 years – monocrystalline would take 6 years to pay back.
Mono-like Technology Proliferates, Efficiency Catches Up with Monocrystalline PERC
In 2025, it will rely on "mono-like" technology to make a comeback. Mono-like isn't true monocrystalline; it uses directional solidification to make the grains in the silicon ingot more aligned, reducing grain boundaries by 40% (traditional poly grain boundary density 15-20/cm², mono-like reduced to 9-12/cm²). This change directly boosts efficiency from 18%-19% to 20%-21%, approaching monocrystalline PERC's 22%.
Lab data from a tier-1 brand: mono-like modules have first-year degradation of 1.8% (traditional poly 2%), power retention after 10 years is 92% (traditional poly 89%). Over 25 years, total generation is 1,200-1,500 kWh more (for a 50kW system). Third-party teardowns found mono-like micro-crack rate < 0.3% (white-label poly can reach 1%-2%), 10-year failure rate 40% lower. A residential user in Zhejiang installed mono-like in 2024. Measured generation duration under low light (early morning 6-8 AM) was 1.2 hours/day, 0.3 hours more than traditional poly, earning an extra 500 yuan/year (selling at 0.45 yuan/kWh).
Small Factories Clear Inventory, Large Factories Rely on Improved Versions to Maintain Presence
The polycrystalline market is reshuffling. In 2023, polycrystalline capacity utilization was only 55% (monocrystalline >90%). By 2025, the shutdown rate of poly lines in small and medium factories may exceed 30% – retrofitting a poly line costs 20 million yuan, small factories can't afford it, so they switch to other businesses. But major players like LONGi, Trina haven't completely withdrawn; they still hold 10%-15% of improved version inventory, distributed through authorized distributors.
This inventory isn't "e-waste": warranty is still 12 years materials + 25 years power (mainstream level), efficiency 19.5%-20%, first-year degradation ≤1.8%. In contrast, small factories, to clear inventory, secretly shorten warranty to 10 years materials + 20 years power. After 25 years, power might only be 65% (large factory improved versions ≥75%). A user in Jiangsu bought cheap poly from a small factory in 2023. Testing in 2024 found a micro-crack rate of 1.2%, annual generation 800 kWh less (50kW system).
Channels Change: Online/Offline Divergence, Service Becomes More Important Than Price
Previously, polycrystalline relied on wholesale volume. By 2025, the online channel share will increase to 30% (was 15% in 2023). But selling poly online is risky: small factories impersonating big brands, parameter inflation are common. A platform monitoring found that in 2024, 40% of poly complaints were "actual efficiency 2% lower than advertised".
A distributor in Shandong started promoting major brands' improved poly in 2024, specifically calculating the "25-year generation account" for users: for the same 50kW, poly earns 2,000 yuan/year less than mono, but the initial cost is 10,000 yuan lower. After 5-year payback, it earns 3,000 yuan more per year. Users hearing "earn more later" increased orders by 25%.
5 Essential Data Metrics
Last year, a user in Shandong ordered poly because it was 1 yuan/W cheaper, but after installation found annual generation was 15% less than expected, failing to pay back in 5 years. Why? Didn't calculate clearly "how much power can be installed per unit area," "how much loss on low-light days," "whether the inverter can handle it."
Poly technology improved in 2025, but data doesn't lie: monocrystalline efficiency 22%, polycrystalline 19%, difference 3%; monocrystalline first-year degradation 2%, polycrystalline 1.8%, difference 0.2% – these differences in the second decimal place, multiplied by 25-year lifespan, mean tens of thousands in profit difference.
How Much Electricity Per Unit Area? Calculate the "Area-Power-Profit" Triangle
The roof size is fixed. Whether to install poly or mono, first check how many watts per square meter. Monocrystalline efficiency is higher. For the same 100㎡ roof, mono can install 22kW (220W/㎡), poly only 19kW (190W/㎡) – a difference of 3kW, equivalent to half a car less.
But don't rush to dismiss it: poly is 0.1 yuan/W cheaper. 19kW costs 3,000 yuan less than 22kW? Wait, need more accurate calculation. E.g., mono 5 yuan/W, poly 4.9 yuan/W. 19kW poly cost: 93,100 yuan. 22kW mono cost: 110,000 yuan. Difference: 16,900 yuan. Assuming annual irradiance 1200 hours, mono annual generation: 26,400 kWh (22kW × 1200h). Poly annual generation: 22,800 kWh (19kW × 1200h). Difference: 3,600 kWh (selling at 0.4 yuan/kWh, lose 1,440 yuan/year).
Now calculate the "payback difference": poly initial cost is 16,900 yuan lower, but earns 1,440 yuan less per year. It takes 11.7 years to break even. If the user plans to hold for 20 years, the extra earnings in the last 8 years can cover it. But if only planning to use for 10 years, mono is more cost-effective. Remember the formula: Area × Efficiency = Installed Capacity; Installed Capacity × Irradiance = Annual Generation; Annual Generation × Electricity Price = Annual Revenue. Then divide the total cost difference by the annual revenue difference to get the payback equilibrium year.
How Much Loss on Low-Light Days? Use IEC Standard Data to Squeeze Out "Marketing Hype"
Poly is often said to perform poorly on cloudy days, but how poorly exactly? Look at the low-light test under IEC 61,853-2 standard – simulating generation performance at dawn (5-7 AM, 200W/㎡ irradiance) and dusk (5-7 PM, 300W/㎡ irradiance).
Data from a third-party testing agency: ordinary poly maintains 85% efficiency at 200W/㎡ irradiance (output 170W/㎡), mono-like can reach 90% (180W/㎡). Based on annual irradiance of 1600 hours, with low-light periods accounting for 20% (320 hours). For a 50kW system (poly area ≈ 263㎡, 50kW ÷ 190W/㎡ ≈ 263㎡):
l Ordinary poly low-light generation: 170W/㎡ × 263㎡ × 320h ≈ 14,500 kWh;
l Mono-like low-light generation: 180W/㎡ × 263㎡ × 320h ≈ 15,200 kWh;
Difference: 700 kWh/year (at 0.4 yuan/kWh, lose 280 yuan).
Some small factory poly only maintains 80% low-light efficiency, losing 4,000 kWh/year (16,000 yuan).
Can the Inverter Handle It? Calculate "Voltage Matching - Overloading Potential" Clearly
Poly and mono have different voltages. Mono operating voltage 38-45V, poly 35-55V – poly voltage range is 10V wider, which affects inverter overloading.
Example: User installs a 15kW inverter. Mono module operating voltage 42V, max input voltage 600V, can series up to 14 panels (14×42=588V), corresponding capacity 14×450W=6300W (6.3kW). Poly module operating voltage 38V, can series 15 panels (15×38=570V), capacity 15×400W=6000W? Wait, poly panels might have lower power, e.g., 400W per panel, 38V. 15 panels: 15×400=6000W, voltage 15×38=570V, below 600V max. Mono 450W, 42V, 14 panels: 14×450=6300W, voltage 14×42=588V.
What Pitfalls are Hidden in the Warranty? Look at "Power Remaining After 25 Years"
Warranty isn't about "how many years," but "how much electricity after 25 years." Mainstream poly warranty is 12 years materials + 25 years power, but power retention rates vary from 75% to 85%.
A small factory poly warranty says "25-year power retention 75%", a large factory improved version says "80%". For a 50kW system:
l Small factory: Power after 25 years = 50kW × 75% = 37.5kW, annual generation 37.5kW × 1000h = 37,500 kWh.
l Large factory: Power after 25 years = 50kW × 80% = 40kW, annual generation 40kW × 1000h = 40,000 kWh.
l Annual difference: 2,500 kWh (at 0.4 yuan/kWh, lose 1,000 yuan), total loss over 25 years: 25,000 yuan.
Some small factories verbally promise "80% after 25 years", but the contract says "not less than 70%". When buying poly, you must check the warranty contract, focus on "minimum power retention rate" and "breach of contract compensation clauses".
Regional Suitability: Use LCOE to Calculate Clearly "Whether This Money is Worth Spending"
LCOE (Levelized Cost of Electricity) = Total Investment ÷ Total Electricity Generation, lower is better. Example for 50kW system:
· Poly: Total investment = 50kW × 4.9 yuan/W = 245,000 yuan; 25-year generation = 50kW × 1000h × (1 - 0.02^25) ≈ 1.24 million kWh (after degradation); LCOE = 245,000 ÷ 1,240,000 ≈ 0.197 yuan/kWh;
· Mono: Total investment = 50kW × 5 yuan/W = 250,000 yuan; 25-year generation = 50kW × 1000h × (1 - 0.02^25) ≈ 1.28 million kWh; LCOE = 250,000 ÷ 1,280,000 ≈ 0.195 yuan/kWh.
Wait? Mono LCOE is lower? But if there is a local subsidy of 0.3 yuan/kWh:
Poly: Annual revenue = (1.24M kWh × 0.4 yuan) + (subsidy 1.24M kWh × 0.3 yuan) = 496,000 + 372,000 = 868,000 yuan? No, LCOE is total investment divided by total generation; subsidy is extra income, should calculate total revenue. Correct calculation: Total revenue = electricity sales + subsidy. Assuming subsidy 0.3 yuan/kWh, poly total revenue = 1.24M kWh × (0.4 + 0.3) = 868,000 yuan. LCOE = 245,000 ÷ (1.24M kWh × (0.4+0.3)/0.4? No, LCOE considers full lifecycle cost. If including subsidies, should recalculate. Perhaps a simpler way is to compare the Net Present Value (NPV).
Or another example: A region with electricity price 0.3 yuan/kWh, no subsidy. Poly LCOE = 245,000 ÷ 1.24M ≈ 0.197 yuan/kWh (below electricity price, profitable); Mono LCOE = 250,000 ÷ 1.28M ≈ 0.195 yuan/kWh (also profitable, but difference small). If electricity price rises to 0.5 yuan/kWh:
· Poly LCOE = 245,000 ÷ 1.24M ≈ 0.197 yuan/kWh (profit = 0.5 - 0.197 = 0.303 yuan/kWh);
· Mono LCOE = 250,000 ÷ 1.28M ≈ 0.195 yuan/kWh (profit = 0.5 - 0.195 = 0.305 yuan/kWh).
The difference is still small. But if poly's initial cost is 0.1 yuan/W lower, saving 5,000 yuan for 50kW, the profit difference will be amplified.
3-Step Screening Method
Last year, a user in Hebei bought polycrystalline modules online claimed to be "large factory improved version." After installation, problems occurred within six months: generation under low light was 20% less than the neighbor's monocrystalline. Year-end inspection found a micro-crack rate of 1.5% (normal poly < 0.3%). Confronting the seller, they said "the contract doesn't guarantee micro-crack compensation."
Such pitfalls will be more common in 2025 – small factories selling white-label products under the "mono-like" banner, with inflated parameters and shortened warranties. To avoid pitfalls when buying poly, don't trust ads, trust data; don't rely on verbal promises, check the contract.
Check the Brand: Don't Believe "No-Name Improved", Only Recognize Tier-1 Technical Models
80% of "improved poly" on the market are small factory OEMs – they lack technology, just coat ordinary poly with a film and dare to call it "mono-like". Truly having improved technology are only 3 tier-1 brands: LONGi, Trina, Jinko (accounting for 90% of global improved poly production capacity).
How to tell if it's a real technical model? Check patents and test reports. LONGi's "Aurora Series" has 12 mono-like directional solidification patents, grain boundary density reduced from traditional 15-20/cm² to 9-12/cm² (third-party test data), micro-crack rate < 0.3% (small factory white-label can reach 1%-2%). Trina's "Stellar Series" passed 2000-hour salt spray test, corrosion rate 0.05% (small factory 0.15%), can be used on coastal roofs for 5 years without yellowing.
A testing agency teardown of a so-called "improved poly" module found the silicon ingot mixed with a large amount of broken silicon material (15% by weight), efficiency 0.5% lower than standard poly (18% vs 18.5%).
Verify Parameters: Don't Just Look at Efficiency, Low-Light and Degradation Data are More Critical
Merchants love to boast "efficiency 19.5%", but what really affects generation are low-light response and degradation rate.
First, low-light: Require the merchant to provide IEC 61,853-2 standard test report (simulating dawn/dusk irradiance). Genuine improved poly maintains ≥90% efficiency at 200W/㎡ irradiance (output 180W/㎡), ordinary poly only 85% (170W/㎡). Based on annual irradiance 1600 hours, low-light accounting for 20% (320 hours), for a 50kW system:
l Improved poly low-light generation: 180W/㎡ × (50kW ÷ 190W/㎡) × 320h ≈ 15,200 kWh;
l Ordinary poly: 170W/㎡ × 263㎡ × 320h ≈ 14,500 kWh;
l Annual difference: 700 kWh (at 0.4 yuan/kWh, lose 280 yuan).
Next, degradation: First-year degradation ≤1.8% (improved poly), ordinary poly ≥2%. After 25 years, an extra 0.2% first-year degradation compounds into a large gap:
l Improved poly 25-year total degradation ≈15% (annual 0.6%), power remaining 85%;
l Ordinary poly ≈18% (annual 0.72%), power remaining 82%;
l 50kW system annual generation difference: 1,500 kWh (85% × 50kW × 1000h = 425,000 kWh vs 82% × 50kW × 1000h = 410,000 kWh). Lose 37,500 yuan over 25 years.
Verify Warranty: Don't Listen to Verbal Promises, Scrutinize These Three Numbers in the Contract
"25-year power warranty" sounds reliable, but the contract might hide traps. Last year, a user in Jiangsu had a contract saying "25-year warranty," but the small factory interpreted it as "free repair if broken during warranty, power not guaranteed."
Must nail down three numbers:
1. Minimum Power Retention Rate: Genuine improved poly warranty says "≥80% after 25 years" (LONGi, Trina), small factory might say "≥70%". For a 50kW system, after 25 years, generation difference: 50kW × (80% - 70%) = 5kW, annual generation less by 5,000 kWh (assuming 1000 hours irradiance). Lose 20,000 yuan over 10 years.
2. Warranty Start Date: Some small factories count from "shipment date," some from "installation date." A 3-month installation delay shortens the warranty by 3 months.
3. Breach of Contract Compensation Ratio: Reputable brands write "compensate 1.2 times the power deficit if not meeting standard," small factories might only compensate "repair cost." A user's poly power was only 70% after 25 years. According to the contract, compensated 5kW × 5 yuan/W × 1.2 = 30,000 yuan, covering the generation loss.