---
title: "Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 665 vs Q-Cells Q.PEAK DUO RSF XL-G11S.3 / BFG 590 - Solar Panel Comparison | ComparePV"
description: "Compare Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 665 vs Q-Cells Q.PEAK DUO RSF XL-G11S.3 / BFG 590 side by side: what actually differs, output when it is hot, thirty-year production, and the full specification."
source: "https://comparepv.com/compare/q-cells-q-peak-duo-ml-g12s-3-bfg-665/qcells-hanwha-q-cells-america-inc-q-peak-duo-rsf-xl-g11s-3-bfg-590"
updated: 2026-09-11
---

# Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 665 vs Q-Cells Q.PEAK DUO RSF XL-G11S.3 / BFG 590

ML-G12S.3 / BFG 665 leads on the differences that matter

The largest is rated power: 75 W more power. 6 of 17 comparable parameters are identical, with 2 more left out because at least one datasheet does not publish them.


## The two panels


| Attribute | A | B |
| --- | --- | --- |
| Panel | [Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 665](https://comparepv.com/panel/q-cells-q-peak-duo-ml-g12s-3-bfg-665) | [Q-Cells Q.PEAK DUO RSF XL-G11S.3 / BFG 590](https://comparepv.com/panel/qcells-hanwha-q-cells-america-inc-q-peak-duo-rsf-xl-g11s-3-bfg-590) |
| Manufacturer | Q-Cells | Q-Cells |
| Power | 665 Wp | 590 Wp |
| Efficiency | 21.40 % | 21.10 % |
| Technology |  | PERC |


## Where they differ

Ranked by how much the difference matters, not by datasheet order.


| Parameter | ML-G12S.3 / BFG 665 | RSF XL-G11S.3 / BFG 590 | Difference |
| --- | --- | --- | --- |
| Rated power | 665 Wp | 590 Wp | +75 W for ML-G12S.3 / BFG 665 |
| Open-circuit voltage | 45.70 V | 53.60 V | 7.90 V apart |
| Short-circuit current | 18.39 A | 13.74 A | 4.65 A apart |
| Module area | 3.106 m² | 2.792 m² | 0.314 m² apart |
| Module efficiency | 21.40 % | 21.10 % | +0.30 pp for ML-G12S.3 / BFG 665 |
| Weight per kWp | 57.4 kg/kWp | 61.7 kg/kWp | -4.3 kg/kWp for ML-G12S.3 / BFG 665 |
| Weight | 38.2 kg | 36.4 kg | -1.8 kg for RSF XL-G11S.3 / BFG 590 |
| Voltage at max power | 38.11 V | 44.96 V | 6.85 V apart |
| Current at max power | 17.45 A | 13.12 A | 4.33 A apart |
| Cell count | 132 | 156 | 24 cells apart |
| Dimensions | 2384x1303x35 mm | 2462x1134x35 mm | 2384x1303x35 mm vs 2462x1134x35 mm |


## Every compared parameter


| Parameter | ML-G12S.3 / BFG 665 | RSF XL-G11S.3 / BFG 590 |
| --- | --- | --- |
| Rated power | 665 Wp | 590 Wp |
| Module efficiency | 21.40 % | 21.10 % |
| Power density | 214.1 Wp/m² | 211.3 Wp/m² |
| Open-circuit voltage | 45.70 V | 53.60 V |
| Voltage at max power | 38.11 V | 44.96 V |
| Short-circuit current | 18.39 A | 13.74 A |
| Current at max power | 17.45 A | 13.12 A |
| Temperature coefficient | -0.340 %/°C | -0.340 %/°C |
| Dimensions | 2384x1303x35 mm | 2462x1134x35 mm |
| Module area | 3.106 m² | 2.792 m² |
| Weight | 38.2 kg | 36.4 kg |
| Weight per kWp | 57.4 kg/kWp | 61.7 kg/kWp |
| Product warranty | 12 yrs | - |
| Performance warranty | 30 yrs | 30 yrs |
| Annual degradation | 0.45 %/yr | 0.45 %/yr |
| Cell technology | - | PERC |
| Cell type | Monocrystalline | Monocrystalline |
| Cell count | 132 | 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 (-0.340 %/°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, ML-G12S.3 / BFG 665:** 21,899 kWh
- **Cumulative output, RSF XL-G11S.3 / BFG 590:** 19,429 kWh
- **Gap:** 2,470 kWh


## Output when hot


| Condition | Cell temperature | ML-G12S.3 / BFG 665 | RSF XL-G11S.3 / BFG 590 | Retained |
| --- | --- | --- | --- | --- |
| Standard test conditions | 25 °C | 665 W | 590 W | 100.0% of rated power |
| Cool, bright day | 40 °C | 631 W | 560 W | 94.9% of rated power |
| Typical summer roof | 55 °C | 597 W | 530 W | 89.8% of rated power |
| Hot roof | 70 °C | 563 W | 500 W | 84.7% of rated power |


## Against the whole database


| Measure | ML-G12S.3 / BFG 665 | RSF XL-G11S.3 / BFG 590 | Out of | Note |
| --- | --- | --- | --- | --- |
| Efficiency | #8,323 | #9,297 | 14,005 | ML-G12S.3 / BFG 665 leads by 974 places |
| Power density | #8,250 | #9,241 | 14,005 | ML-G12S.3 / BFG 665 leads by 991 places |
| Heat behaviour | #8,778 | #8,778 | 14,005 | Tied - the same position in the database |
| Weight | #11,217 | #12,677 | 14,005 | ML-G12S.3 / BFG 665 leads by 1,460 places |
| Warranty | #21 | #21 | 14,005 | Tied - the same position in the database |
| Overall | #2,833 | #8,523 | 14,005 | ML-G12S.3 / BFG 665 leads by 5,690 places |


## Questions


### Which panel is better: Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 665 or Q-Cells Q.PEAK DUO RSF XL-G11S.3 / BFG 590?

According to our database: **Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 665** has higher module efficiency (**21.40%** vs **21.10%**). See the full spec comparison and 30-year energy simulation above for a complete picture.


### What is the efficiency of Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 665 and Q-Cells Q.PEAK DUO RSF XL-G11S.3 / BFG 590?

**Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 665** has a module efficiency of **21.40%**, while **Q-Cells Q.PEAK DUO RSF XL-G11S.3 / BFG 590** is **21.10%**. Higher efficiency means more electricity from the same roof area - useful when space is limited.


### What cell technology does Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 665 use vs Q-Cells Q.PEAK DUO RSF XL-G11S.3 / BFG 590?

**Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 665** uses Monocrystalline cells; **Q-Cells Q.PEAK DUO RSF XL-G11S.3 / BFG 590** uses **PERC**. 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 Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 665 and Q-Cells Q.PEAK DUO RSF XL-G11S.3 / BFG 590?

**Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 665** has a **30 years** power warranty; **Q-Cells Q.PEAK DUO RSF XL-G11S.3 / BFG 590** 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 Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 665 and Q-Cells Q.PEAK DUO RSF XL-G11S.3 / BFG 590 bifacial panels?

Both **Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 665** and **Q-Cells Q.PEAK DUO RSF XL-G11S.3 / BFG 590** 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

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- [Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 665 vs Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 670](https://comparepv.com/compare/q-cells-q-peak-duo-ml-g12s-3-bfg-665/q-cells-q-peak-duo-ml-g12s-3-bfg-670) - One difference: module efficiency
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- [Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 665 vs Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 655](https://comparepv.com/compare/q-cells-q-peak-duo-ml-g12s-3-bfg-665/q-cells-q-peak-duo-ml-g12s-3-bfg-655) - 3 differences, the largest is module efficiency
- [Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 665 vs Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 650](https://comparepv.com/compare/q-cells-q-peak-duo-ml-g12s-3-bfg-665/q-cells-q-peak-duo-ml-g12s-3-bfg-650) - 3 differences, the largest is module efficiency
- [Q-Cells Q.PEAK DUO RSF XL-G11S.3 / BFG 590 vs Q-Cells Q.PEAK DUO RSF XL-G11S.3 / BFG 600](https://comparepv.com/compare/qcells-hanwha-q-cells-america-inc-q-peak-duo-rsf-xl-g11s-3-bfg-590/qcells-hanwha-q-cells-america-inc-q-peak-duo-rsf-xl-g11s-3-bfg-600) - 3 differences, the largest is module efficiency


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Source: https://comparepv.com/compare/q-cells-q-peak-duo-ml-g12s-3-bfg-665/qcells-hanwha-q-cells-america-inc-q-peak-duo-rsf-xl-g11s-3-bfg-590

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.