--- title: "JA Solar JAM66D42-590/MB vs JA Solar JAM66D46-740/LB - Solar Panel Comparison | ComparePV" description: "Compare JA Solar JAM66D42-590/MB vs JA Solar JAM66D46-740/LB side by side: what actually differs, output when it is hot, thirty-year production, and the full specification." source: "https://comparepv.com/compare/ja-solar-jam66d42-590-mb/ja-solar-jam66d46-740-lb" image: "https://comparepv.com/og/compare/panels/ja-solar-jam66d42-590-mb/ja-solar-jam66d46-740-lb.png" updated: 2026-09-11 --- # JA Solar JAM66D42-590/MB vs JA Solar JAM66D46-740/LB JAM66D46-740/LB leads on the differences that matter The largest is module efficiency: 1.00 pp more efficient. 8 of 19 comparable parameters are identical. ## The two panels | Attribute | A | B | | --- | --- | --- | | Panel | [JA Solar JAM66D42-590/MB](https://comparepv.com/panel/ja-solar-jam66d42-590-mb) | [JA Solar JAM66D46-740/LB](https://comparepv.com/panel/ja-solar-jam66d46-740-lb) | | Manufacturer | JA Solar | JA Solar | | Power | 590 Wp | 740 Wp | | Efficiency | 22.80 % | 23.80 % | | Technology | TOPCon | TOPCon | ## Where they differ Ranked by how much the difference matters, not by datasheet order. | Parameter | JAM66D42-590/MB | JAM66D46-740/LB | Difference | | --- | --- | --- | --- | | Module efficiency | 22.80 % | 23.80 % | +1.00 pp for JAM66D46-740/LB | | Rated power | 590 Wp | 740 Wp | +150 W for JAM66D46-740/LB | | Power density | 228.4 Wp/m² | 238.2 Wp/m² | +9.8 Wp/m² for JAM66D46-740/LB | | Weight | 31.8 kg | 38.2 kg | -6.4 kg for JAM66D42-590/MB | | Short-circuit current | 15.31 A | 18.73 A | 3.42 A apart | | Module area | 2.583 m² | 3.106 m² | 0.523 m² apart | | Current at max power | 14.45 A | 17.64 A | 3.19 A apart | | Weight per kWp | 53.9 kg/kWp | 51.6 kg/kWp | -2.3 kg/kWp for JAM66D46-740/LB | | Open-circuit voltage | 48.58 V | 49.80 V | 1.22 V apart | | Dimensions | 2278x1134x30 mm | 2384x1303x33 mm | 2278x1134x30 mm vs 2384x1303x33 mm | | Voltage at max power | 40.84 V | 41.96 V | 1.12 V apart | ## Every compared parameter | Parameter | JAM66D42-590/MB | JAM66D46-740/LB | | --- | --- | --- | | Rated power | 590 Wp | 740 Wp | | Module efficiency | 22.80 % | 23.80 % | | Power density | 228.4 Wp/m² | 238.2 Wp/m² | | Open-circuit voltage | 48.58 V | 49.80 V | | Voltage at max power | 40.84 V | 41.96 V | | Short-circuit current | 15.31 A | 18.73 A | | Current at max power | 14.45 A | 17.64 A | | Temperature coefficient | -0.290 %/°C | -0.290 %/°C | | Dimensions | 2278x1134x30 mm | 2384x1303x33 mm | | Module area | 2.583 m² | 3.106 m² | | Weight | 31.8 kg | 38.2 kg | | Weight per kWp | 53.9 kg/kWp | 51.6 kg/kWp | | Product warranty | 12 yrs | 12 yrs | | Performance warranty | 30 yrs | 30 yrs | | Annual degradation | 0.40 %/yr | 0.40 %/yr | | Cell technology | TOPCon | TOPCon | | Cell type | Monocrystalline | Monocrystalline | | Cell count | 132 | 132 | | Bifacial | Yes | Yes | ## Thirty-year yield Each panel's own declared degradation curve, at 1,200 kWh/kWp a year Same temp coeff. for both panels (-0.290 %/°C), so a warmer roof scales both curves by the same factor: the totals fall together and neither panel gains on the other. - **Cumulative output, JAM66D42-590/MB:** 19,796 kWh - **Cumulative output, JAM66D46-740/LB:** 24,828 kWh - **Gap:** 5,032 kWh ## Output when hot | Condition | Cell temperature | JAM66D42-590/MB | JAM66D46-740/LB | Retained | | --- | --- | --- | --- | --- | | Standard test conditions | 25 °C | 590 W | 740 W | 100.0% of rated power | | Cool, bright day | 40 °C | 564 W | 708 W | 95.7% of rated power | | Typical summer roof | 55 °C | 539 W | 676 W | 91.3% of rated power | | Hot roof | 70 °C | 513 W | 643 W | 87.0% of rated power | ## Against the whole database | Measure | JAM66D42-590/MB | JAM66D46-740/LB | Out of | Note | | --- | --- | --- | --- | --- | | Efficiency | #2,769 | #462 | 14,129 | JAM66D46-740/LB leads by 2,307 places | | Power density | #2,653 | #460 | 14,129 | JAM66D46-740/LB leads by 2,193 places | | Heat behaviour | #2,220 | #2,220 | 14,129 | Tied - the same position in the database | | Weight | #8,099 | #5,026 | 14,129 | JAM66D46-740/LB leads by 3,073 places | | Warranty | #21 | #21 | 14,129 | Tied - the same position in the database | | Overall | #3,852 | #185 | 14,129 | JAM66D46-740/LB leads by 3,667 places | ## Questions ### Which panel is better: JA Solar JAM66D42-590/MB or JA Solar JAM66D46-740/LB? According to our database: **JA Solar JAM66D46-740/LB** has higher module efficiency (**23.80%** vs **22.80%**). See the full spec comparison and 30-year energy simulation above for a complete picture. ### What is the efficiency of JA Solar JAM66D42-590/MB and JA Solar JAM66D46-740/LB? **JA Solar JAM66D42-590/MB** has a module efficiency of **22.80%**, while **JA Solar JAM66D46-740/LB** is **23.80%**. Higher efficiency means more electricity from the same roof area - useful when space is limited. ### What cell technology does JA Solar JAM66D42-590/MB use vs JA Solar JAM66D46-740/LB? **JA Solar JAM66D42-590/MB** uses **TOPCon** cells; **JA Solar JAM66D46-740/LB** uses **TOPCon**. Modern **n-type** technologies (**TOPCon**, **HJT**, BC) typically deliver higher efficiency and lower degradation compared to older **PERC** (p-type) cells. ### What is the warranty on JA Solar JAM66D42-590/MB and JA Solar JAM66D46-740/LB? **JA Solar JAM66D42-590/MB** has a **30 years** power warranty; **JA Solar JAM66D46-740/LB** has a **30 years** power warranty. The power warranty guarantees a minimum percentage of rated output at the end of the warranty period (typically 80**-87%**). Product (materials) warranties are usually shorter. ### Are JA Solar JAM66D42-590/MB and JA Solar JAM66D46-740/LB bifacial panels? Both **JA Solar JAM66D42-590/MB** and **JA Solar JAM66D46-740/LB** are bifacial - they capture reflected light from the ground, which can add 5**-15%** more annual energy on ground-mount or elevated rooftop installations with a light surface beneath. ## Related comparisons - [JA Solar JAM66D42-590/MB vs JA Solar JAM66D42-605/MB](https://comparepv.com/compare/ja-solar-jam66d42-590-mb/ja-solar-jam66d42-605-mb) - 3 differences, the largest is module efficiency - [JA Solar JAM66D42-590/MB vs JA Solar JAM66D42-600/MB](https://comparepv.com/compare/ja-solar-jam66d42-590-mb/ja-solar-jam66d42-600-mb) - 3 differences, the largest is module efficiency - [JA Solar JAM66D42-590/MB vs JA Solar JAM66D42-595/MB](https://comparepv.com/compare/ja-solar-jam66d42-590-mb/ja-solar-jam66d42-595-mb) - One difference: module efficiency - [JA Solar JAM66D42-590/MB vs JA Solar JAM66D42-585/MB](https://comparepv.com/compare/ja-solar-jam66d42-590-mb/ja-solar-jam66d42-585-mb) - One difference: module efficiency - [JA Solar JAM66D42-590/MB vs JA Solar JAM66D42-580/MB](https://comparepv.com/compare/ja-solar-jam66d42-590-mb/ja-solar-jam66d42-580-mb) - 3 differences, the largest is module efficiency - [JA Solar JAM66D46-740/LB vs JA Solar JAM66D46-735/LB](https://comparepv.com/compare/ja-solar-jam66d46-740-lb/ja-solar-jam66d46-735-lb) - The same specification on paper --- Source: https://comparepv.com/compare/ja-solar-jam66d42-590-mb/ja-solar-jam66d46-740-lb Not in this file, on the page: the thirty-year yield curve year by year at a cell temperature you pick and a written summary generated on request.