JA Solar JAM66D46-740/LB vs JA Solar JAM66D42-585/MB
VS
The verdict
JAM66D46-740/LB leads on the differences that matter
The largest is module efficiency: 1.20 pp more efficient. 8 of 19 comparable parameters are identical.
See all 11 differencesHow alike are they
8
of 19 comparable
parameters are identical
parameters are identical
identical
differs
01
11 of 19 parameters
What actually differs
Parameter
JAM66D46-740/LB
JAM66D42-585/MB
Difference
Module efficiency
23.80 %
22.60 %
1.20 pp more efficient
Rated power
740 Wp
585 Wp
155 W more power
Power density
238.2 Wp/m²
226.5 Wp/m²
11.8 Wp/m² higher
Weight
38.2 kg
31.8 kg
6.4 kg lighter
Short-circuit current
18.73 A
15.26 A
3.47 A apart
Module area
3.106 m²
2.583 m²
0.523 m² apart
Weight per kWp
51.6 kg/kWp
54.4 kg/kWp
2.7 kg/kWp lighter
Current at max power
17.64 A
14.40 A
3.24 A apart
Open-circuit voltage
49.80 V
48.38 V
1.42 V apart
Dimensions
2384x1303x33 mm
2278x1134x30 mm
2384x1303x33 mm vs 2278x1134x30 mm
Voltage at max power
41.96 V
40.63 V
1.33 V apart
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 (-0.290 %/°C), so a warmer roof scales both curves by the same factor: the totals fall together and neither panel gains on the other.
JAM66D46-740/LB
24,828 kWh
JAM66D42-585/MB
19,628 kWh
Lifetime gap
5,200 kWh
Output when it is hot
Rated power carried across the range a module actually sees
Scenario
JAM66D46-740/LB
JAM66D42-585/MB
Standard test conditions
25 °C
100.0% of rated power
740 W
585 W
Cool, bright day
40 °C
95.7% of rated power
708 W
560 W
Typical summer roof
55 °C
91.3% of rated power
676 W
534 W
Hot roof
70 °C
87.0% of rated power
643 W
509 W
03
Full specification
Parameter
JAM66D46-740/LB
JAM66D42-585/MB
Difference
Power and efficiency
Rated power
740 Wp
585 Wp
+155 W for JAM66D46-740/LB
Module efficiency
23.80 %
22.60 %
+1.20 pp for JAM66D46-740/LB
Power density
238.2 Wp/m²
226.5 Wp/m²
+11.8 Wp/m² for JAM66D46-740/LB
Open-circuit voltage
49.80 V
48.38 V
1.42 V apart
Voltage at max power
41.96 V
40.63 V
1.33 V apart
Short-circuit current
18.73 A
15.26 A
3.47 A apart
Current at max power
17.64 A
14.40 A
3.24 A apart
Temperature
Temperature coefficient
-0.290 %/°C
-0.290 %/°C
Same
Mechanical
Dimensions
2384x1303x33 mm
2278x1134x30 mm
2384x1303x33 mm vs 2278x1134x30 mm
Module area
3.106 m²
2.583 m²
0.523 m² apart
Weight
38.2 kg
31.8 kg
-6.4 kg for JAM66D42-585/MB
Weight per kWp
51.6 kg/kWp
54.4 kg/kWp
-2.7 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
TOPCon
Same
Cell type
Monocrystalline
Monocrystalline
Same
Cell count
132
132
Same
Bifacial
Yes
Yes
Same
04
14,129 panels
Against the whole database
Efficiency
#462
vs
#3,716
JAM66D46-740/LB leads by 3,254 places
Power density
#460
vs
#3,557
JAM66D46-740/LB leads by 3,097 places
Heat behaviour
#2,220
vs
#2,220
Tied - the same position in the database
Weight
#5,026
vs
#8,749
JAM66D46-740/LB leads by 3,723 places
Warranty
#21
vs
#21
Tied - the same position in the database
Overall
#185
vs
#4,254
JAM66D46-740/LB leads by 4,069 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 JAM66D42-585/MB?
According to our database: JA Solar JAM66D46-740/LB has higher module efficiency (23.80% vs 22.60%). 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 JAM66D42-585/MB?
JA Solar JAM66D46-740/LB has a module efficiency of 23.80%, while JA Solar JAM66D42-585/MB is 22.60%. 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 JAM66D42-585/MB?
JA Solar JAM66D46-740/LB uses TOPCon cells; JA Solar JAM66D42-585/MB uses TOPCon. 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 JAM66D42-585/MB?
JA Solar JAM66D46-740/LB has a 30 years power warranty; JA Solar JAM66D42-585/MB 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 JAM66D42-585/MB bifacial panels?
Both JA Solar JAM66D46-740/LB and JA Solar JAM66D42-585/MB 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 327 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.