--- title: "Silfab SIL-580-XM+-BIFACIAL vs Silfab SIL-640 XL - Solar Panel Comparison | ComparePV" description: "Compare Silfab SIL-580-XM+-BIFACIAL vs Silfab SIL-640 XL side by side: what actually differs, output when it is hot, thirty-year production, and the full specification." source: "https://comparepv.com/compare/silfab-sil-580-xm-bifacial/silfab-sil-640-xl" updated: 2026-09-11 --- # Silfab SIL-580-XM+-BIFACIAL vs Silfab SIL-640 XL 640 XL leads on the differences that matter The largest is rated power: 60 W more power. 9 of 19 comparable parameters are identical. ## The two panels | Attribute | A | B | | --- | --- | --- | | Panel | [Silfab SIL-580-XM+-BIFACIAL](https://comparepv.com/panel/silfab-sil-580-xm-bifacial) | [Silfab SIL-640 XL](https://comparepv.com/panel/silfab-sil-640-xl) | | Manufacturer | Silfab | Silfab | | Power | 580 Wp | 640 Wp | | Efficiency | 22.40 % | 22.92 % | | Technology | N-type | N-type | ## Where they differ Ranked by how much the difference matters, not by datasheet order. | Parameter | 580-XM+-BIFACIAL | 640 XL | Difference | | --- | --- | --- | --- | | Rated power | 580 Wp | 640 Wp | +60 W for 640 XL | | Module efficiency | 22.40 % | 22.92 % | +0.52 pp for 640 XL | | Open-circuit voltage | 52.27 V | 57.76 V | 5.49 V apart | | Module area | 2.581 m² | 2.793 m² | 0.212 m² apart | | Power density | 224.7 Wp/m² | 229.2 Wp/m² | +4.4 Wp/m² for 640 XL | | Weight per kWp | 49.1 kg/kWp | 46.1 kg/kWp | -3.0 kg/kWp for 640 XL | | Voltage at max power | 44.27 V | 48.78 V | 4.51 V apart | | Cell count | 144 | 156 | 12 cells apart | | Weight | 28.5 kg | 29.5 kg | -1.0 kg for 580-XM+-BIFACIAL | | Dimensions | 2278x1133x35 mm | 2465x1133x35 mm | 2278x1133x35 mm vs 2465x1133x35 mm | ## Every compared parameter | Parameter | 580-XM+-BIFACIAL | 640 XL | | --- | --- | --- | | Rated power | 580 Wp | 640 Wp | | Module efficiency | 22.40 % | 22.92 % | | Power density | 224.7 Wp/m² | 229.2 Wp/m² | | Open-circuit voltage | 52.27 V | 57.76 V | | Voltage at max power | 44.27 V | 48.78 V | | Short-circuit current | 13.85 A | 13.76 A | | Current at max power | 13.10 A | 13.12 A | | Temperature coefficient | -0.290 %/°C | -0.290 %/°C | | Dimensions | 2278x1133x35 mm | 2465x1133x35 mm | | Module area | 2.581 m² | 2.793 m² | | Weight | 28.5 kg | 29.5 kg | | Weight per kWp | 49.1 kg/kWp | 46.1 kg/kWp | | Product warranty | 25 yrs | 25 yrs | | Performance warranty | 30 yrs | 30 yrs | | Annual degradation | 0.30 %/yr | 0.30 %/yr | | Cell technology | N-type | N-type | | Cell type | Monocrystalline | Monocrystalline | | Cell count | 144 | 156 | | 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, 580-XM+-BIFACIAL:** 19,554 kWh - **Cumulative output, 640 XL:** 21,577 kWh - **Gap:** 2,023 kWh ## Output when hot | Condition | Cell temperature | 580-XM+-BIFACIAL | 640 XL | Retained | | --- | --- | --- | --- | --- | | Standard test conditions | 25 °C | 580 W | 640 W | 100.0% of rated power | | Cool, bright day | 40 °C | 555 W | 612 W | 95.7% of rated power | | Typical summer roof | 55 °C | 530 W | 584 W | 91.3% of rated power | | Hot roof | 70 °C | 504 W | 556 W | 87.0% of rated power | ## Against the whole database | Measure | 580-XM+-BIFACIAL | 640 XL | Out of | Note | | --- | --- | --- | --- | --- | | Efficiency | #4,774 | #2,350 | 14,005 | 640 XL leads by 2,424 places | | Power density | #4,528 | #2,379 | 14,005 | 640 XL leads by 2,149 places | | Heat behaviour | #2,165 | #2,165 | 14,005 | Tied - the same position in the database | | Weight | #2,767 | #1,004 | 14,005 | 640 XL leads by 1,763 places | | Warranty | #21 | #21 | 14,005 | Tied - the same position in the database | | Overall | #2,018 | #650 | 14,005 | 640 XL leads by 1,368 places | ## Questions ### Which panel is better: Silfab SIL-580-XM+-BIFACIAL or Silfab SIL-640 XL? According to our database: **Silfab SIL-640 XL** has higher module efficiency (**22.92%** vs **22.40%**). See the full spec comparison and 30-year energy simulation above for a complete picture. ### What is the efficiency of Silfab SIL-580-XM+-BIFACIAL and Silfab SIL-640 XL? **Silfab SIL-580-XM+-BIFACIAL** has a module efficiency of **22.40%**, while **Silfab SIL-640 XL** is **22.92%**. Higher efficiency means more electricity from the same roof area - useful when space is limited. ### What cell technology does Silfab SIL-580-XM+-BIFACIAL use vs Silfab SIL-640 XL? **Silfab SIL-580-XM+-BIFACIAL** uses **N-type** cells; **Silfab SIL-640 XL** uses **N-type**. 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 Silfab SIL-580-XM+-BIFACIAL and Silfab SIL-640 XL? **Silfab SIL-580-XM+-BIFACIAL** has a **30 years** power warranty; **Silfab SIL-640 XL** 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 Silfab SIL-580-XM+-BIFACIAL and Silfab SIL-640 XL bifacial panels? Both **Silfab SIL-580-XM+-BIFACIAL** and **Silfab SIL-640 XL** 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 - [Silfab SIL-580-XM+-BIFACIAL vs Silfab SIL-590 XM+](https://comparepv.com/compare/silfab-sil-580-xm-bifacial/silfab-sil-590-xm) - 3 differences, the largest is module efficiency - [Silfab SIL-580-XM+-BIFACIAL vs Silfab SIL-570 XM+ BIFACIAL](https://comparepv.com/compare/silfab-sil-580-xm-bifacial/silfab-sil-570-xm-bifacial) - 3 differences, the largest is module efficiency - [Silfab SIL-580-XM+-BIFACIAL vs Silfab SIL-570 XM+](https://comparepv.com/compare/silfab-sil-580-xm-bifacial/silfab-sil-570-xm) - 3 differences, the largest is module efficiency - [Silfab SIL-580-XM+-BIFACIAL vs Silfab SIL-530 XM](https://comparepv.com/compare/silfab-sil-580-xm-bifacial/silfab-sil-530-xm) - 7 differences, the largest is rated power - [Silfab SIL-580-XM+-BIFACIAL vs Silfab SIL-520 XM](https://comparepv.com/compare/silfab-sil-580-xm-bifacial/silfab-sil-520-xm) - 10 differences, the largest is rated power - [Silfab SIL-580-XM+-BIFACIAL vs Silfab SIL-520 QM](https://comparepv.com/compare/silfab-sil-580-xm-bifacial/silfab-sil-520-qm) - 11 differences, the largest is rated power --- Source: https://comparepv.com/compare/silfab-sil-580-xm-bifacial/silfab-sil-640-xl 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.