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660M vs 640M 16 of 19 identical Swap Change panels

Longi Solar LR7-72HVD-660M vs Longi Solar LR7-72HVD-640M

Longi Solar LR7-72HVD-660M
LR7-72HVD-660M
660 Wp 24.40 % N-type Bifacial
Open panel page Datasheet PDF
VS
Longi Solar LR7-72HVD-640M
LR7-72HVD-640M
640 Wp 23.70 % N-type Bifacial
Open panel page Datasheet PDF
The verdict

660M leads on the differences that matter

The largest is module efficiency: 0.70 pp more efficient. 16 of 19 comparable parameters are identical.

See all 3 differences
How alike are they
16 of 19 comparable
parameters are identical
identical differs
01

What actually differs

3 of 19 parameters
Parameter 660M 640M Difference
Module efficiency 24.40 % 23.70 % 0.70 pp more efficient
Power density 244.3 Wp/m² 236.9 Wp/m² 7.4 Wp/m² higher
Rated power 660 Wp 640 Wp 20 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
Same temp coeff. for both panels (-0.260 %/°C), so a warmer roof scales both curves by the same factor: the totals fall together and neither panel gains on the other.
660M
22,317 kWh
640M
21,640 kWh
Lifetime gap
677 kWh
Output when it is hot
Rated power carried across the range a module actually sees
Scenario 660M 640M
Standard test conditions 25 °C 100.0% of rated power 660 W 640 W
Cool, bright day 40 °C 96.1% of rated power 634 W 615 W
Typical summer roof 55 °C 92.2% of rated power 609 W 590 W
Hot roof 70 °C 88.3% of rated power 583 W 565 W
03

Full specification

Parameter 660M 640M Difference
Power and efficiency
Rated power 660 Wp 640 Wp +20 W for 660M
Module efficiency 24.40 % 23.70 % +0.70 pp for 660M
Power density 244.3 Wp/m² 236.9 Wp/m² +7.4 Wp/m² for 660M
Open-circuit voltage 54.42 V 54.02 V Effectively the same
Voltage at max power 45.07 V 44.67 V Effectively the same
Short-circuit current 15.30 A 14.98 A Effectively the same
Current at max power 14.65 A 14.33 A Effectively the same
Temperature
Temperature coefficient -0.260 %/°C -0.260 %/°C Same
Mechanical
Dimensions 2382x1134x30 mm 2382x1134x30 mm Same
Module area 2.701 m² 2.701 m² Same
Weight 33.5 kg 33.5 kg Same
Weight per kWp 50.8 kg/kWp 52.3 kg/kWp Effectively the same
Warranty and degradation
Product warranty 15 yrs 15 yrs Same
Performance warranty 30 yrs 30 yrs Same
Annual degradation 0.35 %/yr 0.35 %/yr Same
Technology
Cell technology N-type N-type Same
Cell type Monocrystalline Monocrystalline Same
Cell count 144 144 Same
Bifacial Yes Yes Same
04

Against the whole database

14,005 panels
Efficiency
#99 vs #517
660M leads by 418 places
Power density
#88 vs #521
660M leads by 433 places
Heat behaviour
#511 vs #511
Tied - the same position in the database
Weight
#4,172 vs #5,829
660M leads by 1,657 places
Warranty
#21 vs #21
Tied - the same position in the database
Overall
#576 vs #1,271
660M leads by 695 places
05

More useful comparisons

Open the full database
Same series, other bin
Longi Solar LR7-72HVD-660M vs Longi Solar LR7-72HVD-665M
One difference: module efficiency
Same series, other bin
Longi Solar LR7-72HVD-660M vs Longi Solar LR7-72HVD-655M
One difference: module efficiency
Same series, other bin
Longi Solar LR7-72HVD-660M vs Longi Solar LR7-72HVD-650M
3 differences, the largest is module efficiency
Same series, other bin
Longi Solar LR7-72HVD-660M vs Longi Solar LR7-72HVD-645M
3 differences, the largest is module efficiency
Same manufacturer
Longi Solar LR7-72HVD-660M vs Longi Solar LR7-72HVHF-670M
6 differences, the largest is weight
Same manufacturer
Longi Solar LR7-72HVD-660M vs Longi Solar LR8-66HYD-670M
10 differences, the largest is module efficiency
06

Written summary

07

Questions about this pairing

Which panel is better: Longi Solar LR7-72HVD-660M or Longi Solar LR7-72HVD-640M?
According to our database: Longi Solar LR7-72HVD-660M has higher module efficiency (24.40% vs 23.70%). See the full spec comparison and 30-year energy simulation above for a complete picture.
What is the efficiency of Longi Solar LR7-72HVD-660M and Longi Solar LR7-72HVD-640M?
Longi Solar LR7-72HVD-660M has a module efficiency of 24.40%, while Longi Solar LR7-72HVD-640M is 23.70%. Higher efficiency means more electricity from the same roof area - useful when space is limited.
What cell technology does Longi Solar LR7-72HVD-660M use vs Longi Solar LR7-72HVD-640M?
Longi Solar LR7-72HVD-660M uses N-type cells; Longi Solar LR7-72HVD-640M 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 Longi Solar LR7-72HVD-660M and Longi Solar LR7-72HVD-640M?
Longi Solar LR7-72HVD-660M has a 30 years power warranty; Longi Solar LR7-72HVD-640M 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 Longi Solar LR7-72HVD-660M and Longi Solar LR7-72HVD-640M bifacial panels?
Both Longi Solar LR7-72HVD-660M and Longi Solar LR7-72HVD-640M 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.