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660 vs 665 17 of 18 identical Swap Change panels

Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 660 vs Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 665

Q.PEAK DUO ML-G12S.3 / BFG 660
660 Wp 21.20 % Bifacial
Open panel page Datasheet PDF
VS
Q.PEAK DUO ML-G12S.3 / BFG 665
665 Wp 21.40 % Bifacial
Open panel page Datasheet PDF
The verdict

665 leads on the differences that matter

The largest is module efficiency: 0.20 pp more efficient. 17 of 18 comparable parameters are identical, with 1 more left out because at least one datasheet does not publish it.

See the one difference
How alike are they
17 of 18 comparable
parameters are identical
identical differs not published
01

What actually differs

1 of 18 parameters
Parameter 660 665 Difference
Module efficiency 21.20 % 21.40 % 0.20 pp more efficient
02

What it means on a roof

Thirty years of production
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.
660
21,734 kWh
665
21,899 kWh
Lifetime gap
165 kWh
Output when it is hot
Rated power carried across the range a module actually sees
Scenario 660 665
Standard test conditions 25 °C 100.0% of rated power 660 W 665 W
Cool, bright day 40 °C 94.9% of rated power 626 W 631 W
Typical summer roof 55 °C 89.8% of rated power 593 W 597 W
Hot roof 70 °C 84.7% of rated power 559 W 563 W
03

Full specification

Parameter 660 665 Difference
Power and efficiency
Rated power 660 Wp 665 Wp Effectively the same
Module efficiency 21.20 % 21.40 % +0.20 pp for 665
Power density 212.5 Wp/m² 214.1 Wp/m² Effectively the same
Open-circuit voltage 45.68 V 45.70 V Effectively the same
Voltage at max power 37.94 V 38.11 V Effectively the same
Short-circuit current 18.36 A 18.39 A Effectively the same
Current at max power 17.39 A 17.45 A Effectively the same
Temperature
Temperature coefficient -0.340 %/°C -0.340 %/°C Same
Mechanical
Dimensions 2384x1303x35 mm 2384x1303x35 mm Same
Module area 3.106 m² 3.106 m² Same
Weight 38.2 kg 38.2 kg Same
Weight per kWp 57.9 kg/kWp 57.4 kg/kWp Effectively the same
Warranty and degradation
Product warranty 12 yrs 12 yrs Same
Performance warranty 30 yrs 30 yrs Same
Annual degradation 0.45 %/yr 0.45 %/yr Same
Technology
Cell technology - - Neither datasheet publishes this
Cell type Monocrystalline Monocrystalline Same
Cell count 132 132 Same
Bifacial Yes Yes Same
04

Against the whole database

14,005 panels
Efficiency
#9,076 vs #8,323
665 leads by 753 places
Power density
#8,959 vs #8,250
665 leads by 709 places
Heat behaviour
#8,778 vs #8,778
Tied - the same position in the database
Weight
#11,467 vs #11,217
665 leads by 250 places
Warranty
#21 vs #21
Tied - the same position in the database
Overall
#3,228 vs #2,833
665 leads by 395 places
05

More useful comparisons

Open the full database
Same series, other bin
Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 660 vs Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 675
3 differences, the largest is module efficiency
Same series, other bin
Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 660 vs Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 670
3 differences, the largest is module efficiency
Same series, other bin
Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 660 vs Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 655
The same specification on paper
Same series, other bin
Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 660 vs Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 650
3 differences, the largest is module efficiency
Same manufacturer
Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 660 vs Q-Cells Q.TRON XL-G2.3 / BFG 645
14 differences, the largest is module efficiency
Same manufacturer
Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 660 vs Q-Cells Q.TRON XL-G2.3 / BFG 640
14 differences, the largest is module efficiency
06

Written summary

07

Questions about this pairing

Which panel is better: Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 660 or Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 665?
According to our database: Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 665 has higher module efficiency (21.40% vs 21.20%). 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 660 and Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 665?
Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 660 has a module efficiency of 21.20%, while Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 665 is 21.40%. 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 660 use vs Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 665?
Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 660 uses Monocrystalline cells; Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 665 uses Monocrystalline. 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 660 and Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 665?
Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 660 has a 30 years power warranty; Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 665 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 660 and Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 665 bifacial panels?
Both Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 660 and Q-Cells Q.PEAK DUO ML-G12S.3 / BFG 665 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.

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Every figure here is from the manufacturers' own datasheets - a dash means the value is not published, never an estimate. The thirty-year projection and the temperature scenarios are calculations from those figures, and each states its assumption above.