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520 XM BIFACIAL vs 640 XL 8 of 18 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 Incomplete
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. 8 of 18 comparable parameters are identical, with 1 more left out because at least one datasheet does not publish it.

See all 10 differences
How alike are they
8 of 18 comparable
parameters are identical
identical differs not published
01

What actually differs

10 of 18 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
Declared first-year losses, with 0.40% a year afterwards assumed for both panels, 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
17,260 kWh
640 XL
21,243 kWh
Lifetime gap
3,983 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 Not published by Silfab
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
Same series, other bin
Silfab
Silfab SIL-520 XM BIFACIAL vs Silfab SIL-520-XM-BIFACIAL
The same specification on paper
Same series, other bin
Silfab
Silfab SIL-640 XL vs Silfab SIL-630 XL
3 differences, the largest is module efficiency
Same series, other bin
Silfab
Silfab SIL-640 XL vs Silfab SIL-620 XL
3 differences, the largest is module efficiency
Same manufacturer
Silfab
Silfab SIL-520 XM BIFACIAL vs Silfab SIL-590 XM+
10 differences, the largest is module efficiency
Same manufacturer
Silfab
Silfab SIL-520 XM BIFACIAL vs Silfab SIL-580-XM+-BIFACIAL
9 differences, the largest is rated power
Same manufacturer
Silfab
Silfab SIL-520 XM BIFACIAL vs Silfab SIL-570 XM+ BIFACIAL
8 differences, the largest is rated power
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.