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635 vs 645 15 of 19 identical Swap Change panels

Q-Cells Q.TRON XL-G2.3 / BFG 635 vs Q-Cells Q.TRON XL-G2.3 / BFG 645

Q-Cells Q.TRON XL-G2.3 / BFG 635
Q.TRON XL-G2.3 / BFG 635
635 Wp 22.70 % N-type Bifacial
Open panel page Datasheet PDF
VS
Q-Cells Q.TRON XL-G2.3 / BFG 645
Q.TRON XL-G2.3 / BFG 645
645 Wp 23.10 % N-type Bifacial
Open panel page Datasheet PDF
The verdict

645 leads on the differences that matter

The largest is module efficiency: 0.40 pp more efficient. 15 of 19 comparable parameters are identical.

See all 4 differences
How alike are they
15 of 19 comparable
parameters are identical
identical differs
01

What actually differs

4 of 19 parameters
Parameter 635 645 Difference
Module efficiency 22.70 % 23.10 % 0.40 pp more efficient
Temperature coefficient -0.300 %/°C -0.290 %/°C 0.010 %/°C better in heat
Power density 227.4 Wp/m² 231.0 Wp/m² 3.6 Wp/m² higher
Rated power 635 Wp 645 Wp 10 W more power
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
635
21,423 kWh
645
21,761 kWh
Lifetime gap
338 kWh
Output when it is hot
Rated power carried across the range a module actually sees
Scenario 635 645
Standard test conditions 25 °C 100.0% of rated power 635 W 645 W
Cool, bright day 40 °C 95.5% of rated power 606 W 617 W
Typical summer roof 55 °C 91.0% of rated power 578 W 589 W
Hot roof 70 °C 86.5% of rated power 549 W 561 W
03

Full specification

Parameter 635 645 Difference
Power and efficiency
Rated power 635 Wp 645 Wp +10 W for 645
Module efficiency 22.70 % 23.10 % +0.40 pp for 645
Power density 227.4 Wp/m² 231.0 Wp/m² +3.6 Wp/m² for 645
Open-circuit voltage 57.51 V 58.07 V Effectively the same
Voltage at max power 48.09 V 48.47 V Effectively the same
Short-circuit current 13.93 A 14.05 A Effectively the same
Current at max power 13.21 A 13.31 A Effectively the same
Temperature
Temperature coefficient -0.300 %/°C -0.290 %/°C +0.010 %/°C for 645
Mechanical
Dimensions 2462x1134x35 mm 2462x1134x35 mm Same
Module area 2.792 m² 2.792 m² Same
Weight 35.4 kg 35.4 kg Same
Weight per kWp 55.7 kg/kWp 54.9 kg/kWp Effectively the same
Warranty and degradation
Product warranty 12 yrs 12 yrs Same
Performance warranty 30 yrs 30 yrs Same
Annual degradation 0.33 %/yr 0.33 %/yr Same
Technology
Cell technology N-type N-type Same
Cell type Monocrystalline Monocrystalline Same
Cell count 156 156 Same
Bifacial Yes Yes Same
04

Against the whole database

14,005 panels
Efficiency
#3,307 vs #1,570
645 leads by 1,737 places
Power density
#3,192 vs #1,629
645 leads by 1,563 places
Heat behaviour
#6,093 vs #2,165
645 leads by 3,928 places
Weight
#10,141 vs #9,271
645 leads by 870 places
Warranty
#21 vs #21
Tied - the same position in the database
Overall
#2,404 vs #1,826
645 leads by 578 places
05

More useful comparisons

Open the full database
Same series, other bin
Q-Cells Q.TRON XL-G2.3 / BFG 635 vs Q-Cells Q.TRON XL-G2.3 / BFG 640
2 differences, the largest is temperature coefficient
Same series, other bin
Q-Cells Q.TRON XL-G2.3 / BFG 635 vs Q-Cells Q.TRON XL-G2.3 / BFG 630
The same specification on paper
Same series, other bin
Q-Cells Q.TRON XL-G2.3 / BFG 635 vs Q-Cells Q.TRON XL-G2.3 / BFG 625
3 differences, the largest is module efficiency
Same series, other bin
Q-Cells Q.TRON XL-G2.3 / BFG 635 vs Q-Cells Q.TRON XL-G2.3 / BFG 620
3 differences, the largest is module efficiency
Same series, other bin
Q-Cells Q.TRON XL-G2.3 / BFG 635 vs Q-Cells Q.TRON XL-G2.3 / BFG 615
4 differences, the largest is module efficiency
Same series, other bin
Q-Cells Q.TRON XL-G2.3 / BFG 635 vs Q-Cells Q.TRON XL-G2.3 / BFG 610
5 differences, the largest is module efficiency
06

Written summary

07

Questions about this pairing

Which panel is better: Q-Cells Q.TRON XL-G2.3 / BFG 635 or Q-Cells Q.TRON XL-G2.3 / BFG 645?
According to our database: Q-Cells Q.TRON XL-G2.3 / BFG 645 has higher module efficiency (23.10% vs 22.70%); Q-Cells Q.TRON XL-G2.3 / BFG 645 tolerates heat better (temp coeff -0.290%/°C vs -0.300%/°C). See the full spec comparison and 30-year energy simulation above for a complete picture.
What is the efficiency of Q-Cells Q.TRON XL-G2.3 / BFG 635 and Q-Cells Q.TRON XL-G2.3 / BFG 645?
Q-Cells Q.TRON XL-G2.3 / BFG 635 has a module efficiency of 22.70%, while Q-Cells Q.TRON XL-G2.3 / BFG 645 is 23.10%. Higher efficiency means more electricity from the same roof area - useful when space is limited.
What cell technology does Q-Cells Q.TRON XL-G2.3 / BFG 635 use vs Q-Cells Q.TRON XL-G2.3 / BFG 645?
Q-Cells Q.TRON XL-G2.3 / BFG 635 uses N-type cells; Q-Cells Q.TRON XL-G2.3 / BFG 645 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 Q-Cells Q.TRON XL-G2.3 / BFG 635 and Q-Cells Q.TRON XL-G2.3 / BFG 645?
Q-Cells Q.TRON XL-G2.3 / BFG 635 has a 30 years power warranty; Q-Cells Q.TRON XL-G2.3 / BFG 645 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.TRON XL-G2.3 / BFG 635 and Q-Cells Q.TRON XL-G2.3 / BFG 645 bifacial panels?
Both Q-Cells Q.TRON XL-G2.3 / BFG 635 and Q-Cells Q.TRON XL-G2.3 / BFG 645 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.