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640M vs 665M 16 of 19 identical Swap Change panels

Longi Solar LR7-72HVDF-640M vs Longi Solar LR7-72HVDF-665M

Longi Solar LR7-72HVDF-640M
LR7-72HVDF-640M
640 Wp 23.70 % N-type Bifacial
Open panel page Datasheet PDF
VS
Longi Solar LR7-72HVDF-665M
LR7-72HVDF-665M
665 Wp 24.60 % N-type Bifacial
Open panel page Datasheet PDF
The verdict

665M leads on the differences that matter

The largest is module efficiency: 0.90 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 640M 665M Difference
Module efficiency 23.70 % 24.60 % 0.90 pp more efficient
Power density 236.9 Wp/m² 246.2 Wp/m² 9.3 Wp/m² higher
Rated power 640 Wp 665 Wp 25 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.
640M
21,640 kWh
665M
22,486 kWh
Lifetime gap
846 kWh
Output when it is hot
Rated power carried across the range a module actually sees
Scenario 640M 665M
Standard test conditions 25 °C 100.0% of rated power 640 W 665 W
Cool, bright day 40 °C 96.1% of rated power 615 W 639 W
Typical summer roof 55 °C 92.2% of rated power 590 W 613 W
Hot roof 70 °C 88.3% of rated power 565 W 587 W
03

Full specification

Parameter 640M 665M Difference
Power and efficiency
Rated power 640 Wp 665 Wp +25 W for 665M
Module efficiency 23.70 % 24.60 % +0.90 pp for 665M
Power density 236.9 Wp/m² 246.2 Wp/m² +9.3 Wp/m² for 665M
Open-circuit voltage 54.02 V 54.52 V Effectively the same
Voltage at max power 44.67 V 45.17 V Effectively the same
Short-circuit current 14.98 A 15.35 A Effectively the same
Current at max power 14.33 A 14.72 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 52.3 kg/kWp 50.4 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
#517 vs #51
665M leads by 466 places
Power density
#521 vs #42
665M leads by 479 places
Heat behaviour
#511 vs #511
Tied - the same position in the database
Weight
#5,829 vs #3,742
665M leads by 2,087 places
Warranty
#21 vs #21
Tied - the same position in the database
Overall
#1,271 vs #414
665M leads by 857 places
05

More useful comparisons

Open the full database
Same series, other bin
Longi Solar LR7-72HVDF-640M vs Longi Solar LR7-72HVDF-660M
3 differences, the largest is module efficiency
Same series, other bin
Longi Solar LR7-72HVDF-640M vs Longi Solar LR7-72HVDF-655M
3 differences, the largest is module efficiency
Same series, other bin
Longi Solar LR7-72HVDF-640M vs Longi Solar LR7-72HVDF-650M
3 differences, the largest is module efficiency
Same series, other bin
Longi Solar LR7-72HVDF-640M vs Longi Solar LR7-72HVDF-645M
One difference: module efficiency
Same manufacturer
Longi Solar LR7-72HVDF-640M vs Longi Solar LR7-72HVHF-670M
8 differences, the largest is module efficiency
Same manufacturer
Longi Solar LR7-72HVDF-640M vs Longi Solar LR8-66HYD-670M
11 differences, the largest is module efficiency
06

Written summary

07

Questions about this pairing

Which panel is better: Longi Solar LR7-72HVDF-640M or Longi Solar LR7-72HVDF-665M?
According to our database: Longi Solar LR7-72HVDF-665M has higher module efficiency (24.60% 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 LR7-72HVDF-640M and Longi Solar LR7-72HVDF-665M?
Longi Solar LR7-72HVDF-640M has a module efficiency of 23.70%, while Longi Solar LR7-72HVDF-665M is 24.60%. Higher efficiency means more electricity from the same roof area - useful when space is limited.
What cell technology does Longi Solar LR7-72HVDF-640M use vs Longi Solar LR7-72HVDF-665M?
Longi Solar LR7-72HVDF-640M uses N-type cells; Longi Solar LR7-72HVDF-665M 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 LR7-72HVDF-640M and Longi Solar LR7-72HVDF-665M?
Longi Solar LR7-72HVDF-640M has a 30 years power warranty; Longi Solar LR7-72HVDF-665M 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 LR7-72HVDF-640M and Longi Solar LR7-72HVDF-665M bifacial panels?
Both Longi Solar LR7-72HVDF-640M and Longi Solar LR7-72HVDF-665M 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.

Shop prices: See 177 Longi Solar offers

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.