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520-XM-BIFACIAL vs 640 XL 9 of 19 identical Swap Change panels

Silfab SIL-520-XM-BIFACIAL vs Silfab SIL-640 XL

Silfab
SIL-520-XM-BIFACIAL
520 Wp 21.90 % N-type Bifacial
Open panel page Datasheet PDF
VS
Silfab
SIL-640 XL
640 Wp 22.92 % N-type Bifacial
Open panel page Datasheet PDF
The verdict

640 XL leads on the differences that matter

The largest is module efficiency: 1.02 pp more efficient. 9 of 19 comparable parameters are identical.

See all 10 differences
How alike are they
9 of 19 comparable
parameters are identical
identical differs
01

What actually differs

10 of 19 parameters
Parameter 520-XM-BIFACIAL 640 XL Difference
Module efficiency 21.90 % 22.92 % 1.02 pp more efficient
Rated power 520 Wp 640 Wp 120 W more power
Power density 218.8 Wp/m² 229.2 Wp/m² 10.4 Wp/m² higher
Weight 26.2 kg 29.5 kg 3.3 kg lighter
Open-circuit voltage 47.52 V 57.76 V 10.24 V apart
Module area 2.377 m² 2.793 m² 0.416 m² apart
Weight per kWp 50.4 kg/kWp 46.1 kg/kWp 4.3 kg/kWp lighter
Voltage at max power 40.48 V 48.78 V 8.30 V apart
Cell count 132 156 24 cells apart
Dimensions 2098x1133x35 mm 2465x1133x35 mm 2098x1133x35 mm vs 2465x1133x35 mm
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 (-0.290 %/°C), so a warmer roof scales both curves by the same factor: the totals fall together and neither panel gains on the other.
520-XM-BIFACIAL
17,531 kWh
640 XL
21,577 kWh
Lifetime gap
4,046 kWh
Output when it is hot
Rated power carried across the range a module actually sees
Scenario 520-XM-BIFACIAL 640 XL
Standard test conditions 25 °C 100.0% of rated power 520 W 640 W
Cool, bright day 40 °C 95.7% of rated power 497 W 612 W
Typical summer roof 55 °C 91.3% of rated power 475 W 584 W
Hot roof 70 °C 87.0% of rated power 452 W 556 W
03

Full specification

Parameter 520-XM-BIFACIAL 640 XL Difference
Power and efficiency
Rated power 520 Wp 640 Wp +120 W for 640 XL
Module efficiency 21.90 % 22.92 % +1.02 pp for 640 XL
Power density 218.8 Wp/m² 229.2 Wp/m² +10.4 Wp/m² for 640 XL
Open-circuit voltage 47.52 V 57.76 V 10.24 V apart
Voltage at max power 40.48 V 48.78 V 8.30 V apart
Short-circuit current 13.65 A 13.76 A Effectively the same
Current at max power 12.85 A 13.12 A Effectively the same
Temperature
Temperature coefficient -0.290 %/°C -0.290 %/°C Same
Mechanical
Dimensions 2098x1133x35 mm 2465x1133x35 mm 2098x1133x35 mm vs 2465x1133x35 mm
Module area 2.377 m² 2.793 m² 0.416 m² apart
Weight 26.2 kg 29.5 kg -3.3 kg for 520-XM-BIFACIAL
Weight per kWp 50.4 kg/kWp 46.1 kg/kWp -4.3 kg/kWp for 640 XL
Warranty and degradation
Product warranty 25 yrs 25 yrs Same
Performance warranty 30 yrs 30 yrs Same
Annual degradation 0.30 %/yr 0.30 %/yr Same
Technology
Cell technology N-type N-type Same
Cell type Monocrystalline Monocrystalline Same
Cell count 132 156 24 cells apart
Bifacial Yes Yes Same
04

Against the whole database

14,005 panels
Efficiency
#6,783 vs #2,350
640 XL leads by 4,433 places
Power density
#6,837 vs #2,379
640 XL leads by 4,458 places
Heat behaviour
#2,165 vs #2,165
Tied - the same position in the database
Weight
#3,761 vs #1,004
640 XL leads by 2,757 places
Warranty
#21 vs #21
Tied - the same position in the database
Overall
#4,485 vs #650
640 XL leads by 3,835 places
05

More useful comparisons

Open the full database
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Silfab SIL-520-XM-BIFACIAL vs Silfab SIL-580-XM+-BIFACIAL
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Silfab SIL-520-XM-BIFACIAL vs Silfab SIL-570 XM+ BIFACIAL
8 differences, the largest is rated power
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Silfab SIL-520-XM-BIFACIAL vs Silfab SIL-540-XM-BIFACIAL
4 differences, the largest is module efficiency
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Silfab
Silfab SIL-520-XM-BIFACIAL vs Silfab SIL-520 XM BIFACIAL
The same specification on paper
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Silfab
Silfab SIL-640 XL vs Silfab SIL-630 XL
3 differences, the largest is module efficiency
Same series, other bin
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Silfab SIL-640 XL vs Silfab SIL-620 XL
3 differences, the largest is module efficiency
06

Written summary

07

Questions about this pairing

Which panel is better: Silfab SIL-520-XM-BIFACIAL or Silfab SIL-640 XL?
According to our database: Silfab SIL-640 XL has higher module efficiency (22.92% vs 21.90%). See the full spec comparison and 30-year energy simulation above for a complete picture.
What is the efficiency of Silfab SIL-520-XM-BIFACIAL and Silfab SIL-640 XL?
Silfab SIL-520-XM-BIFACIAL has a module efficiency of 21.90%, 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-520-XM-BIFACIAL use vs Silfab SIL-640 XL?
Silfab SIL-520-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-520-XM-BIFACIAL and Silfab SIL-640 XL?
Silfab SIL-520-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-520-XM-BIFACIAL and Silfab SIL-640 XL bifacial panels?
Both Silfab SIL-520-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.

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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.