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66HVD-665M vs 66HYD-665M 17 of 18 identical Swap Change panels

Longi Solar LR8-66HVD-665M vs Longi Solar LR8-66HYD-665M

Longi Solar LR8-66HVD-665M
LR8-66HVD-665M
665 Wp 24.62 % Back Contact Bifacial
Open panel page Datasheet PDF
VS
Longi Solar LR8-66HYD-665M
LR8-66HYD-665M
665 Wp 24.60 % Back Contact Bifacial Incomplete
Open panel page Datasheet PDF
The verdict

66HVD-665M leads on the differences that matter

The largest is product warranty: 3 yrs longer. 17 of 18 comparable parameters are identical, with 1 more left out because at least one datasheet does not publish it.

See the one difference
How alike are they
17 of 18 comparable
parameters are identical
identical differs not published
01

What actually differs

1 of 18 parameters
Parameter 66HVD-665M 66HYD-665M Difference
Product warranty 15 yrs 12 yrs 3 yrs longer
02

What it means on a roof

Thirty years of production
A 1.0% first-year loss then 0.40% a year, assumed for both panels, 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.
66HVD-665M
22,312 kWh
66HYD-665M
22,312 kWh
Lifetime gap
No difference
Output when it is hot
Rated power carried across the range a module actually sees
Scenario 66HVD-665M 66HYD-665M
Standard test conditions 25 °C 100.0% of rated power 665 W 665 W
Cool, bright day 40 °C 96.1% of rated power 639 W 639 W
Typical summer roof 55 °C 92.2% of rated power 613 W 613 W
Hot roof 70 °C 88.3% of rated power 587 W 587 W
03

Full specification

Parameter 66HVD-665M 66HYD-665M Difference
Power and efficiency
Rated power 665 Wp 665 Wp Same
Module efficiency 24.62 % 24.60 % Effectively the same
Power density 246.2 Wp/m² 246.2 Wp/m² Same
Open-circuit voltage 50.02 V 50.02 V Same
Voltage at max power 41.28 V 41.28 V Same
Short-circuit current 16.78 A 16.78 A Same
Current at max power 16.11 A 16.11 A 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 50.4 kg/kWp 50.4 kg/kWp Same
Warranty and degradation
Product warranty 15 yrs 12 yrs +3 yrs for 66HVD-665M
Performance warranty 30 yrs 30 yrs Same
Annual degradation 0.35 %/yr - Not published by Longi Solar
Technology
Cell technology Back Contact Back Contact Same
Cell type Monocrystalline Monocrystalline Same
Cell count 132 132 Same
Bifacial Yes Yes Same
04

Against the whole database

14,129 panels
Efficiency
#47 vs #58
66HVD-665M leads by 11 places
Power density
#47 vs #47
Tied - the same position in the database
Heat behaviour
#515 vs #515
Tied - the same position in the database
Weight
#3,759 vs #3,759
Tied - the same position in the database
Warranty
#21 vs #21
Tied - the same position in the database
Overall
#402 vs #654
66HVD-665M leads by 252 places
05

More useful comparisons

Open the full database
Same series, other bin
Longi Solar LR8-66HVD-665M vs Longi Solar LR8-66HVD-660M
The same specification on paper
Same series, other bin
Longi Solar LR8-66HVD-665M vs Longi Solar LR8-66HVD-655M
3 differences, the largest is module efficiency
Same series, other bin
Longi Solar LR8-66HVD-665M vs Longi Solar LR8-66HVD-650M
3 differences, the largest is module efficiency
Same series, other bin
Longi Solar LR8-66HVD-665M vs Longi Solar LR8-66HVD-645M
3 differences, the largest is module efficiency
Same series, other bin
Longi Solar LR8-66HVD-665M vs Longi Solar LR8-66HVD-640M
3 differences, the largest is module efficiency
Same series, other bin
Longi Solar LR8-66HYD-665M vs Longi Solar LR8-66HYD-670M
One difference: module efficiency
06

Written summary

07

Questions about this pairing

Which panel is better: Longi Solar LR8-66HVD-665M or Longi Solar LR8-66HYD-665M?
According to our database: Longi Solar LR8-66HVD-665M has higher module efficiency (24.62% vs 24.60%). See the full spec comparison and 30-year energy simulation above for a complete picture.
What is the efficiency of Longi Solar LR8-66HVD-665M and Longi Solar LR8-66HYD-665M?
Longi Solar LR8-66HVD-665M has a module efficiency of 24.62%, while Longi Solar LR8-66HYD-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 LR8-66HVD-665M use vs Longi Solar LR8-66HYD-665M?
Longi Solar LR8-66HVD-665M uses Back Contact cells; Longi Solar LR8-66HYD-665M uses Back Contact. 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 LR8-66HVD-665M and Longi Solar LR8-66HYD-665M?
Longi Solar LR8-66HVD-665M has a 30 years power warranty; Longi Solar LR8-66HYD-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 LR8-66HVD-665M and Longi Solar LR8-66HYD-665M bifacial panels?
Both Longi Solar LR8-66HVD-665M and Longi Solar LR8-66HYD-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.

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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.