JA Solar JAM66D46-740/LB vs JA Solar JAM78D40-620/MB/1500V
VS
The verdict
JAM66D46-740/LB leads on the differences that matter
The largest is module efficiency: 1.60 pp more efficient. 5 of 19 comparable parameters are identical.
See all 14 differencesHow alike are they
5
of 19 comparable
parameters are identical
parameters are identical
identical
differs
01
14 of 19 parameters
What actually differs
Parameter
JAM66D46-740/LB
JAM78D40-620/MB/1500V
Difference
Module efficiency
23.80 %
22.20 %
1.60 pp more efficient
Rated power
740 Wp
620 Wp
120 W more power
Power density
238.2 Wp/m²
221.8 Wp/m²
16.4 Wp/m² higher
Weight
38.2 kg
34.6 kg
3.6 kg lighter
Open-circuit voltage
49.80 V
55.34 V
5.54 V apart
Short-circuit current
18.73 A
14.30 A
4.43 A apart
Module area
3.106 m²
2.795 m²
0.311 m² apart
Weight per kWp
51.6 kg/kWp
55.8 kg/kWp
4.2 kg/kWp lighter
Temperature coefficient
-0.290 %/°C
-0.300 %/°C
0.010 %/°C better in heat
Cell technology
TOPCon
N-type
TOPCon vs N-type
Voltage at max power
41.96 V
46.20 V
4.24 V apart
Current at max power
17.64 A
13.42 A
4.22 A apart
Cell count
132
156
24 cells apart
Dimensions
2384x1303x33 mm
2465x1134x35 mm
2384x1303x33 mm vs 2465x1134x35 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
JAM66D46-740/LB
24,828 kWh
JAM78D40-620/MB/1500V
20,802 kWh
Lifetime gap
4,026 kWh
Output when it is hot
Rated power carried across the range a module actually sees
Scenario
JAM66D46-740/LB
JAM78D40-620/MB/1500V
Standard test conditions
25 °C
100.0% of rated power
740 W
620 W
Cool, bright day
40 °C
95.5% of rated power
708 W
592 W
Typical summer roof
55 °C
91.0% of rated power
676 W
564 W
Hot roof
70 °C
86.5% of rated power
643 W
536 W
03
Full specification
Parameter
JAM66D46-740/LB
JAM78D40-620/MB/1500V
Difference
Power and efficiency
Rated power
740 Wp
620 Wp
+120 W for JAM66D46-740/LB
Module efficiency
23.80 %
22.20 %
+1.60 pp for JAM66D46-740/LB
Power density
238.2 Wp/m²
221.8 Wp/m²
+16.4 Wp/m² for JAM66D46-740/LB
Open-circuit voltage
49.80 V
55.34 V
5.54 V apart
Voltage at max power
41.96 V
46.20 V
4.24 V apart
Short-circuit current
18.73 A
14.30 A
4.43 A apart
Current at max power
17.64 A
13.42 A
4.22 A apart
Temperature
Temperature coefficient
-0.290 %/°C
-0.300 %/°C
+0.010 %/°C for JAM66D46-740/LB
Mechanical
Dimensions
2384x1303x33 mm
2465x1134x35 mm
2384x1303x33 mm vs 2465x1134x35 mm
Module area
3.106 m²
2.795 m²
0.311 m² apart
Weight
38.2 kg
34.6 kg
-3.6 kg for JAM78D40-620/MB/1500V
Weight per kWp
51.6 kg/kWp
55.8 kg/kWp
-4.2 kg/kWp for JAM66D46-740/LB
Warranty and degradation
Product warranty
12 yrs
12 yrs
Same
Performance warranty
30 yrs
30 yrs
Same
Annual degradation
0.40 %/yr
0.40 %/yr
Same
Technology
Cell technology
TOPCon
N-type
TOPCon vs N-type
Cell type
Monocrystalline
Monocrystalline
Same
Cell count
132
156
24 cells apart
Bifacial
Yes
Yes
Same
04
14,005 panels
Against the whole database
Efficiency
#433
vs
#5,817
JAM66D46-740/LB leads by 5,384 places
Power density
#431
vs
#5,869
JAM66D46-740/LB leads by 5,438 places
Heat behaviour
#2,165
vs
#6,093
JAM66D46-740/LB leads by 3,928 places
Weight
#4,997
vs
#10,192
JAM66D46-740/LB leads by 5,195 places
Warranty
#21
vs
#21
Tied - the same position in the database
Overall
#185
vs
#3,457
JAM66D46-740/LB leads by 3,272 places
05
Open the full database
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06
Written summary
Checking cache...
07
Questions about this pairing
Which panel is better: JA Solar JAM66D46-740/LB or JA Solar JAM78D40-620/MB/1500V?
According to our database: JA Solar JAM66D46-740/LB has higher module efficiency (23.80% vs 22.20%); JA Solar JAM66D46-740/LB tolerates heat better (temp coeff -0.290%/°C vs -0.300%/°C). See the full spec comparison and 30-year energy simulation above for a complete picture.
What is the efficiency of JA Solar JAM66D46-740/LB and JA Solar JAM78D40-620/MB/1500V?
JA Solar JAM66D46-740/LB has a module efficiency of 23.80%, while JA Solar JAM78D40-620/MB/1500V is 22.20%. Higher efficiency means more electricity from the same roof area - useful when space is limited.
What cell technology does JA Solar JAM66D46-740/LB use vs JA Solar JAM78D40-620/MB/1500V?
JA Solar JAM66D46-740/LB uses TOPCon cells; JA Solar JAM78D40-620/MB/1500V 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 JA Solar JAM66D46-740/LB and JA Solar JAM78D40-620/MB/1500V?
JA Solar JAM66D46-740/LB has a 30 years power warranty; JA Solar JAM78D40-620/MB/1500V 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 JA Solar JAM66D46-740/LB and JA Solar JAM78D40-620/MB/1500V bifacial panels?
Both JA Solar JAM66D46-740/LB and JA Solar JAM78D40-620/MB/1500V 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 393 JA 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.