--- title: "JA Solar JAM72D40-615/LB vs JA Solar JAM72D42-635/LB - Solar Panel Comparison | ComparePV" description: "Compare JA Solar JAM72D40-615/LB vs JA Solar JAM72D42-635/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-jam72d40-615-lb/ja-solar-jam72d42-635-lb" updated: 2026-09-11 --- # JA Solar JAM72D40-615/LB vs JA Solar JAM72D42-635/LB JAM72D40-615/LB leads on the differences that matter The largest is module efficiency: 0.50 pp more efficient. 11 of 19 comparable parameters are identical. ## The two panels | Attribute | A | B | | --- | --- | --- | | Panel | [JA Solar JAM72D40-615/LB](https://comparepv.com/panel/ja-solar-jam72d40-615-lb) | [JA Solar JAM72D42-635/LB](https://comparepv.com/panel/ja-solar-jam72d42-635-lb) | | Manufacturer | JA Solar | JA Solar | | Power | 615 Wp | 635 Wp | | Efficiency | 23.20 % | 22.70 % | | Technology | TOPCon | TOPCon | ## Where they differ Ranked by how much the difference matters, not by datasheet order. | Parameter | JAM72D40-615/LB | JAM72D42-635/LB | Difference | | --- | --- | --- | --- | | Module efficiency | 23.20 % | 22.70 % | +0.50 pp for JAM72D40-615/LB | | Rated power | 615 Wp | 635 Wp | +20 W for JAM72D42-635/LB | | Module area | 2.646 m² | 2.795 m² | 0.150 m² apart | | Power density | 232.5 Wp/m² | 227.2 Wp/m² | +5.3 Wp/m² for JAM72D40-615/LB | | Weight | 32.5 kg | 34.6 kg | -2.1 kg for JAM72D40-615/LB | | Short-circuit current | 14.61 A | 15.26 A | 0.65 A apart | | Dimensions | 2333x1134x30 mm | 2465x1134x30 mm | 2333x1134x30 mm vs 2465x1134x30 mm | | Current at max power | 13.89 A | 14.40 A | 0.51 A apart | ## Every compared parameter | Parameter | JAM72D40-615/LB | JAM72D42-635/LB | | --- | --- | --- | | Rated power | 615 Wp | 635 Wp | | Module efficiency | 23.20 % | 22.70 % | | Power density | 232.5 Wp/m² | 227.2 Wp/m² | | Open-circuit voltage | 53.00 V | 52.67 V | | Voltage at max power | 44.28 V | 44.10 V | | Short-circuit current | 14.61 A | 15.26 A | | Current at max power | 13.89 A | 14.40 A | | Temperature coefficient | -0.290 %/°C | -0.290 %/°C | | Dimensions | 2333x1134x30 mm | 2465x1134x30 mm | | Module area | 2.646 m² | 2.795 m² | | Weight | 32.5 kg | 34.6 kg | | Weight per kWp | 52.8 kg/kWp | 54.5 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 | 144 | 144 | | 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, JAM72D40-615/LB:** 20,634 kWh - **Cumulative output, JAM72D42-635/LB:** 21,306 kWh - **Gap:** 672 kWh ## Output when hot | Condition | Cell temperature | JAM72D40-615/LB | JAM72D42-635/LB | Retained | | --- | --- | --- | --- | --- | | Standard test conditions | 25 °C | 615 W | 635 W | 100.0% of rated power | | Cool, bright day | 40 °C | 588 W | 607 W | 95.7% of rated power | | Typical summer roof | 55 °C | 561 W | 580 W | 91.3% of rated power | | Hot roof | 70 °C | 535 W | 552 W | 87.0% of rated power | ## Against the whole database | Measure | JAM72D40-615/LB | JAM72D42-635/LB | Out of | Note | | --- | --- | --- | --- | --- | | Efficiency | #1,306 | #3,307 | 14,005 | JAM72D40-615/LB leads by 2,001 places | | Power density | #1,249 | #3,252 | 14,005 | JAM72D40-615/LB leads by 2,003 places | | Heat behaviour | #2,165 | #2,165 | 14,005 | Tied - the same position in the database | | Weight | #6,546 | #8,832 | 14,005 | JAM72D40-615/LB leads by 2,286 places | | Warranty | #21 | #21 | 14,005 | Tied - the same position in the database | | Overall | #2,486 | #2,396 | 14,005 | JAM72D42-635/LB leads by 90 places | ## Questions ### Which panel is better: JA Solar JAM72D40-615/LB or JA Solar JAM72D42-635/LB? According to our database: **JA Solar JAM72D40-615/LB** has higher module efficiency (**23.20%** vs **22.70%**). See the full spec comparison and 30-year energy simulation above for a complete picture. ### What is the efficiency of JA Solar JAM72D40-615/LB and JA Solar JAM72D42-635/LB? **JA Solar JAM72D40-615/LB** has a module efficiency of **23.20%**, while **JA Solar JAM72D42-635/LB** is **22.70%**. Higher efficiency means more electricity from the same roof area - useful when space is limited. ### What cell technology does JA Solar JAM72D40-615/LB use vs JA Solar JAM72D42-635/LB? **JA Solar JAM72D40-615/LB** uses **TOPCon** cells; **JA Solar JAM72D42-635/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 JAM72D40-615/LB and JA Solar JAM72D42-635/LB? **JA Solar JAM72D40-615/LB** has a **30 years** power warranty; **JA Solar JAM72D42-635/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 JAM72D40-615/LB and JA Solar JAM72D42-635/LB bifacial panels? Both **JA Solar JAM72D40-615/LB** and **JA Solar JAM72D42-635/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 JAM72D40-615/LB vs JA Solar JAM72D42-650/LB](https://comparepv.com/compare/ja-solar-jam72d40-615-lb/ja-solar-jam72d42-650-lb) - 6 differences, the largest is rated power - [JA Solar JAM72D40-615/LB vs JA Solar JAM72D42-645/LB](https://comparepv.com/compare/ja-solar-jam72d40-615-lb/ja-solar-jam72d42-645-lb) - 6 differences, the largest is rated power - [JA Solar JAM72D40-615/LB vs JA Solar JAM72D42-640/LB](https://comparepv.com/compare/ja-solar-jam72d40-615-lb/ja-solar-jam72d42-640-lb) - 8 differences, the largest is rated power - [JA Solar JAM72D40-615/LB vs JA Solar JAM72D42-630/LB](https://comparepv.com/compare/ja-solar-jam72d40-615-lb/ja-solar-jam72d42-630-lb) - 8 differences, the largest is module efficiency - [JA Solar JAM72D40-615/LB vs JA Solar JAM72D42-625/LB](https://comparepv.com/compare/ja-solar-jam72d40-615-lb/ja-solar-jam72d42-625-lb) - 8 differences, the largest is module efficiency - [JA Solar JAM72D40-615/LB vs JA Solar JAM72D40-610/LB](https://comparepv.com/compare/ja-solar-jam72d40-615-lb/ja-solar-jam72d40-610-lb) - The same specification on paper --- Source: https://comparepv.com/compare/ja-solar-jam72d40-615-lb/ja-solar-jam72d42-635-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.