--- title: "JA Solar JS400 120M6 HJT DG 400W Solar Panel - Specs & Review | ComparePV" description: "JA Solar JS400 120M6 HJT DG 400W solar panel. Specs: 21.96% efficiency, Monocrystalline cells, dimensions, warranty and temperature coefficient." source: "https://comparepv.com/panel/ja-solar-js400-120m6-hjt-dg" updated: 2026-09-11 --- # JA Solar JS400 120M6 HJT DG Middle of its segment, heavy for its output 113 panels in the segment HJT 400-450 W ## Identity - **Manufacturer:** JA Solar - **Model:** JS400 120M6 HJT DG - **Series:** JS 120M6 HJT DG - **Rated power:** 400 W - **Cell technology:** HJT - **Bifacial:** yes ## How it compares Compared against segment HJT 400-450 W (113 panels). | Measure | This panel | Segment median | Standing | Rank | | --- | --- | --- | --- | --- | | Power (Wp) | 400 W | 435 W | Weak - bottom 4% | | | 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 (kg) | 22.8 kg | 23.0 kg | Weak - bottom 15% | | | Performance warranty | 30 yrs | 30 yrs | Typical | 21 | ### Full peer table | Measure | This panel | Segment median | Standing | 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 | ### Watch out for - **57.0 kg per kWp** - Bottom 15% of the HJT 400-450 W segment, against a median of 52.4. - **Not ideal for:** Weight-limited structures. ## Specification ### Electrical - **Rated power (Pmax):** 400 W - **Efficiency:** 21.96 % - **Voltage at Pmax (Vmp):** 38.43 V - **Current at Pmax (Imp):** 10.41 A - **Open-circuit voltage (Voc):** 45.45 V - **Short-circuit current (Isc):** 11.13 A - **Max system voltage:** 1500 V ### Temperature - **Temperature coefficient of Pmax:** -0.240 %/degC - **Temperature coefficient of Voc:** -0.220 %/degC - **Temperature coefficient of Isc:** 0.047 %/degC - **NOCT:** 45 degC ### Cell and construction - **Cell type:** Monocrystalline - **Cell technology:** HJT - **Cell count:** 120 - **Bifacial:** yes - **Bifacial gain:** 25.00 ### Physical - **Length:** 1755 mm - **Width:** 1038 mm - **Thickness:** 30 mm - **Weight:** 22.8 kg - **Area:** 1.82 m2 - **Power density:** 219.6 Wp/m2 ### Warranty and degradation - **Product warranty:** 30 years - **Performance warranty:** 30 years - **Output guaranteed at end of warranty:** 82.0 % - **First-year degradation:** 2.00 % - **Annual degradation:** 0.55 % - **Output after 30 years:** 328 W ## Rank in the whole catalogue | Measure | Position | | --- | --- | | Efficiency | 6741 of 14005 | | Power density | 6698 of 14005 | | Temperature coefficient | 13 of 14005 | | Weight | 10998 of 14005 | | Warranty | 21 of 14005 | ## Pros - **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. ## Cons - **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. ## About this series 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. ## Notable figures - 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 ## Questions ### 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. ## Datasheet [Manufacturer datasheet (PDF)](https://comparepv.com/datasheets/1-9db6a9bbc387.pdf) ## Alternatives | Panel | Power | How it differs | | --- | --- | --- | | [Luxor Solar LX-440M/182-108+GG](https://comparepv.com/panel/luxor-solar-lx-440m-182-108-gg) | 440 W | +40 W, +1.1 pp | | [Just Solar JST-EDMH-(445-465)W-TD (450W class)](https://comparepv.com/panel/just-solar-jst-edmh-445-465-w-td-450w-class) | 450 W | +50 W, hotter, +1.1 pp | | [Q-SUN Solar QNN182-HG450-54](https://comparepv.com/panel/qn-solar-pv-limited-qnn182-hg450-54) | 450 W | +50 W, hotter, +1.1 pp | | [Huayao HY440-N108BDD](https://comparepv.com/panel/huayao-hy440-n108bdd) | 450 W | +50 W, hotter, +1.1 pp | | [BYD NLBK-27-450](https://comparepv.com/panel/byd-nlbk-27-450) | 450 W | +50 W, hotter, +1.1 pp | | [Renesola RS41-450NBG-E3](https://comparepv.com/panel/renesola-rs41-450nbg-e3) | 450 W | +50 W, hotter, +1.1 pp | | [JA Solar JS380 120M6 HJT DG](https://comparepv.com/panel/ja-solar-js380-120m6-hjt-dg) | 380 W | -20 W, -1.1 pp | | [JA Solar JS385 120M6 HJT DG](https://comparepv.com/panel/ja-solar-js385-120m6-hjt-dg) | 385 W | -15 W, -0.8 pp | | [JA Solar JS390 120M6 HJT DG](https://comparepv.com/panel/ja-solar-js390-120m6-hjt-dg) | 390 W | -10 W, -0.6 pp | | [JA Solar JS395 120M6 HJT DG](https://comparepv.com/panel/ja-solar-js395-120m6-hjt-dg) | 395 W | -0.3 pp | | [Longi Solar LR7-54HJD-510M](https://comparepv.com/panel/longi-lr7-54hjd-510m) | 510 W | +110 W, +3.0 pp | | [AIKO AIKO-A495-MCE54Mw](https://comparepv.com/panel/aiko-aiko-a495-mce54mw) | 495 W | +95 W, hotter, +2.8 pp | | [Longi Solar LR7-54HJD-505M](https://comparepv.com/panel/longi-lr7-54hjd-505m) | 505 W | +105 W, +2.7 pp | | [AIKO AIKO-A490-MCE54Mw](https://comparepv.com/panel/aiko-aiko-a490-mce54mw) | 490 W | +90 W, hotter, +2.5 pp | | [Longi Solar LR7-54HJD-500M](https://comparepv.com/panel/longi-lr7-54hjd-500m) | 500 W | +100 W, +2.5 pp | | [Talesun CIPRO-TN9C54M-500W](https://comparepv.com/panel/talesun-cipro-tn9c54m-500w) | 500 W | +100 W, hotter, +2.5 pp | --- Source: https://comparepv.com/panel/ja-solar-js400-120m6-hjt-dg Not in this file, on the page: the I-V and temperature curves lifted from the manufacturer's datasheet, a thirty-year output simulator, a bifacial gain calculator and alternatives filtered by how closely they match these dimensions.