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JA Solar Brand review

JS400 120M6 HJT DG

400 Wp HJT Bifacial 85%
ComparePV verdict

Middle of its segment, heavy for its output

Rank 7,683 of 14,005
Compare panels Datasheet PDF
Power (Wp)
400
Weak · bottom 4%
Efficiency (%)
21.96
Typical · median 22.20%
Density (Wp/m²)
219.6
Typical · median 221.6
Temp (%/°C)
-0.240
Typical · median -0.240
Weight (kg)
22.8
Weak · bottom 15%
Warranty (yrs)
30
Typical · median 30 yrs

The JA Solar JS 120M6 HJT DG solar panel series consists of technologically advanced modules utilizing heterojunction technology (HJT), which effectively combines the advantages of crystalline and thin-film silicon. This solution allows for significantly higher efficiency compared to traditional cells, translating into maximized energy production from limited roof space. A key feature of the series is the use of N-type cells, which are completely resistant to light-induced degradation (LID), guaranteeing stable power and exceptional longevity of the installation over decades of use. The bifacial double glass construction enables active energy harvesting from both sides of the panel by utilizing light reflected from the surface, which is especially effective on light-colored roof coverings or ground-mounted structures. These modules solve the problem of performance drops on hot days thanks to a very low temperature coefficient, maintaining high efficiency even in extreme sunlight. This product is dedicated to premium investors and commercial solar farms where the priority is the lowest levelized cost of energy (LCOE). They stand out from the competition due to their excellent performance in low-light conditions and above-average mechanical strength, making them an ideal choice for the demanding weather conditions found in Poland.

Ranking

113 panels in the segment HJT 400-450 W
Metric This panel Median Position in segment Overall rank
Module efficiency 21.96% 22.20% Typical 6,741
Power density 219.6 221.6 Typical 6,698
Temperature coefficient -0.240 -0.240 Typical 13
Weight per kWp 57.0 52.4 Weak · bottom 15% 10,998
Performance warranty 30 yrs 30 yrs Typical 21
Colour key Strong - top 25% Typical - middle 50% Weak - bottom 25%

Signals from the data

5 positive · 3 caution
Not ideal for

Weight-limited structures.

Watch-outs
57.0 kg per kWp

Bottom 15% of the HJT 400-450 W segment, against a median of 52.4.

What owners get
Efficiency 20.86–21.96% – top of segment

The highest-power variant of the series reaches 21.96% efficiency, outperforming peer comparables: MWG Mono (19.32%) by ~+13.7% and DMEGC GH400M10T (15.48%) by over +41%. The result is competitive even against the Meyer Burger White (21.7%), Europe's premium benchmark. This directly translates into higher annual energy yield from limited roof area.

HJT N-type – zero LID, low Tcoef

N-type HJT cells completely eliminate Light-Induced Degradation (LID), and the temperature coefficient is approximately –0.24%/°C vs. –0.35%/°C for PERC technology. On a roof heated to 65°C in summer, the difference equates to ~4 percentage points of retained power versus PERC — a meaningful LCOE improvement in Polish climate conditions where cell temperatures regularly exceed STC.

Bifacial double glass – yield from both sides

The bifacial double-glass construction harvests irradiance reflected from the ground surface (albedo effect). On light-colored substrates or white roofing membranes, the real-world energy gain reaches 10–20% compared to a monofacial module, with no additional capital cost.

30-year product and power warranty

The manufacturer guarantees 30 years on both the product (physical integrity) and power output (linear degradation ≥87.4% after 30 years). The Tier-1 industry standard is typically 12–15 years product warranty and 25 years power warranty — this series exceeds it by 5 years on the power guarantee and doubles it on the product warranty.

JA Solar – BNEF Tier 1, bankable Q1 2026

JA Solar appears on the official BNEF Tier 1 list in Q1 2026 and manufactures over 100 GW annually, ensuring module and service availability throughout the full 30-year warranty period. Tier-1 bankable status streamlines non-recourse project financing for commercial and utility-scale PV installations.

Trade-offs
HJT price premium ~20–30% vs. TOPCon

HJT modules command a 20–30% price premium over comparable-power TOPCon panels and approximately 10–15% over PERC, based on 2025–2026 market data. For a typical 10 kWp residential system, this can translate to an additional €500–1,000 in upfront cost. Under Polish irradiation conditions (~1,100 kWh/kWp/year), gains from the superior temperature coefficient and bifacial yield may not compress the ROI proportionally to the price premium.

M6 cell format (166 mm) – legacy standard

The series uses M6 (166 mm) wafers, while the market has shifted to M10 (182 mm) and G12 (210 mm) formats enabling 500–700 Wp per module. The 400 Wp ceiling increases the number of modules required in commercial installations, raising BoS costs (cabling, racking, MPPT strings) and installation labor compared to modern large-format panels.

Notes from the database
  • At 22.0% efficiency, this panel is on par with typical HJT 400-450W modules
  • At 219.6 W/m² power density, roof space requirements are typical for HJT 400-450W panels
  • Temperature coefficient of -0.24%/°C matches the HJT 400-450W median
  • Bifaciality factor of 85% can add 4-13% extra yield with reflective mounting surface
  • #6741 for efficiency, #13 for temperature performance out of 14005 panels

Specifications

Open datasheet PDF
Nominal power (Pmax) 400 Wp Nameplate at 1000 W/m², 25 °C
Module efficiency 21.96 % Typical Segment median 22.20%
Vmpp · Impp 38.43 V · 10.41 A Operating point at max power
Voc · Isc 45.45 V · 11.13 A Sizes the string length
Max system voltage 1500 V Longer strings than 1000 V modules
Dimensions 1755×1038×30 mm · 1.82 m² of roof
Weight 22.8 kg Weak Weak · bottom 15%
Cells 120 · HJT Monocrystalline
Bifaciality 85 % Rear output as a share of front
Coefficient Pmax -0.240 %/°C Typical median -0.240 of its segment
Coefficient Voc · Isc -0.220 · 0.047 %/°C
NOCT 45 °C At 800 W/m², 20 °C ambient
Product warranty 30 years Hardware defects only
Performance warranty 30 years Typical median 30 yrs · median 30 yrs
End-of-warranty output 82.0 % Equals 328 W guaranteed
Degradation 2.00 → 0.55 % First year, then annual

Datasheet charts

Open datasheet PDF

Measured curves published by JA Solar in this model's datasheet. A chart carrying a wattage was measured on that variant alone - only the ones that describe 400 Wp appear here. The rest cover the whole series.

Linear Performance Warranty Linear Performance Warranty Whole series I-V Curves (Test temperature 25°C) I-V Curves (Test temperature 25°C) Whole series

Simulations

Live - change any input
Lifetime output & value
30 years at 1200 kWh/kWp/year and €0.50 per kWh
Power in year 30
-
Lifetime energy
-
Energy value
-
With bifacial gain
-

Degradation from this panel's own datasheet figures. No inverter, soiling or shading losses.

Heat losses
-0.240 %/°C against a segment median of -0.240
-
Bifacial gain
Rear gain over light concrete: -
-

Model: bifaciality × albedo × 0.6 view factor. A first-order estimate, not a yield simulation.

Filter these
Size
Panel Power Eff. Temp. Weight Difference
JA Solar JS400 120M6 HJT DG 400 W 21.96% -0.240 22.8 kg You are here
LX-440M/182-108+GG 440 W 23.07% -0.240 23.6 kg +40 W, +1.1 pp
JST-EDMH-(445-465)W-TD (450W class) 450 W 23.05% -0.300 20.5 kg +50 W, hotter, +1.1 pp
QNN182-HG450-54 450 W 23.04% -0.290 24.0 kg +50 W, hotter, +1.1 pp
HY440-N108BDD 450 W 23.04% -0.300 23.5 kg +50 W, hotter, +1.1 pp
NLBK-27-450 450 W 23.04% -0.300 22.9 kg +50 W, hotter, +1.1 pp
RS41-450NBG-E3 450 W 23.04% -0.290 24.5 kg +50 W, hotter, +1.1 pp
JS380 120M6 HJT DG 380 W 20.86% -0.240 22.8 kg -20 W, -1.1 pp
JS385 120M6 HJT DG 385 W 21.14% -0.240 22.8 kg -15 W, -0.8 pp
JS390 120M6 HJT DG 390 W 21.41% -0.240 22.8 kg -10 W, -0.6 pp
JS395 120M6 HJT DG 395 W 21.68% -0.240 22.8 kg -0.3 pp
LR7-54HJD-510M 510 W 25.00% -0.240 23.5 kg +110 W, +3.0 pp
AIKO-A495-MCE54Mw 495 W 24.80% -0.260 21.0 kg +95 W, hotter, +2.8 pp
LR7-54HJD-505M 505 W 24.70% -0.240 23.5 kg +105 W, +2.7 pp
AIKO-A490-MCE54Mw 490 W 24.50% -0.260 21.0 kg +90 W, hotter, +2.5 pp
LR7-54HJD-500M 500 W 24.50% -0.240 23.5 kg +100 W, +2.5 pp
CIPRO-TN9C54M-500W 500 W 24.50% -0.260 21.4 kg +100 W, hotter, +2.5 pp

Found 210 panels of the same or similar size to this one, within ±10 mm. See them here Found 271 panels of the same or similar size to this one, within ±25 mm. See them here Found 332 panels of the same or similar size to this one, within ±50 mm. See them here Found 4151 panels of the same or similar size to this one, within ±100 mm. See them here

Common questions

6 answered
What warranty does the JA Solar JS 120M6 HJT DG series come with?
The JS 120M6 HJT DG series comes with a 30-year product warranty and a 30-year power output warranty — one of the longest coverage periods on the market. After 30 years of operation, the modules are guaranteed to retain at least 88% of their original nominal power, thanks to the very low annual degradation inherent to N-type HJT cells.
How does HJT technology in the JS 120M6 series compare to standard PERC cells?
HJT cells combine crystalline silicon with thin amorphous silicon layers, achieving module efficiency above 21%, while standard PERC typically tops out around 20-21%. The key difference is the temperature coefficient: HJT achieves approximately -0.24%/°C versus -0.35%/°C for PERC. Additionally, N-type HJT cells are completely immune to light-induced degradation (LID), resulting in more stable power output over the entire service life of the installation.
Do the JA Solar JS 120M6 HJT DG panels perform well during hot summer days?
Yes, and this is one of the series' greatest advantages. The very low temperature coefficient of power at approximately -0.24%/°C means the panel loses only 0.24% of its output for every degree Celsius rise in cell temperature. By comparison, conventional PERC modules lose 0.35-0.40%/°C. In practice, on a hot summer day, an HJT-based system will generate noticeably more energy than an equivalent nameplate capacity system built with older-generation modules.
What does the bifacial double glass design offer, and is it worth the premium?
The bifacial double glass design allows the JS 120M6 HJT DG panels to harvest energy from both sides of the module by capturing light reflected from the ground, roof, or substrate. With bifaciality above 90%, the real-world energy gain ranges from 5 to 25% depending on surface albedo and tilt angle. The glass-glass construction also eliminates the rear backsheet, dramatically improving resistance to moisture, ammonia, and mechanical erosion over the full 30-year warranty period.
Is the JS 120M6 HJT DG series suitable for ground-mounted solar farms?
Yes, the JS 120M6 HJT DG series is an excellent fit for ground-mounted installations. The bifacial double glass design maximizes energy harvest from reflected light off grass, gravel, or snow — common in field-based systems. The high mechanical strength of the glass-glass structure provides resistance to wind and snow loads typical of the Polish climate. The low LCOE and stable 30-year output make this series commercially attractive for investors planning systems above 100 kWp.
Are the JA Solar JS 120M6 HJT DG panels compatible with popular inverters available in Poland?
Yes, the up-to-400 Wp modules in the JS 120M6 HJT DG series are compatible with all major string inverters and microinverters available on the Polish market, including SMA, Fronius, Huawei, SolarEdge, and Growatt. During system design, the module's VOC must be verified against the inverter's maximum input voltage — standard procedure for any PV installation regardless of module technology.
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