JA Solar JAM78S30-590/MR vs JA Solar JAM66D46-740/LB
VS
The verdict
JAM66D46-740/LB leads on the differences that matter
The largest is module efficiency: 2.70 pp more efficient. 3 of 19 comparable parameters are identical.
See all 16 differencesHow alike are they
3
of 19 comparable
parameters are identical
parameters are identical
identical
differs
01
16 of 19 parameters
What actually differs
Parameter
JAM78S30-590/MR
JAM66D46-740/LB
Difference
Module efficiency
21.10 %
23.80 %
2.70 pp more efficient
Temperature coefficient
-0.350 %/°C
-0.290 %/°C
0.060 %/°C better in heat
Rated power
590 Wp
740 Wp
150 W more power
Power density
211.1 Wp/m²
238.2 Wp/m²
27.2 Wp/m² higher
Performance warranty
25 yrs
30 yrs
5 yrs longer
Annual degradation
0.55 %/yr
0.40 %/yr
0.15 %/yr slower
Weight
30.5 kg
38.2 kg
7.7 kg lighter
Short-circuit current
13.93 A
18.73 A
4.80 A apart
Module area
2.795 m²
3.106 m²
0.311 m² apart
Open-circuit voltage
53.30 V
49.80 V
3.50 V apart
Cell technology
PERC
TOPCon
PERC vs TOPCon
Current at max power
13.17 A
17.64 A
4.47 A apart
Cell count
156
132
24 cells apart
Bifacial
No
Yes
No vs Yes
Voltage at max power
44.80 V
41.96 V
2.84 V apart
Dimensions
2465x1134x35 mm
2384x1303x33 mm
2465x1134x35 mm vs 2384x1303x33 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
JAM78S30-590/MR
19,121 kWh
JAM66D46-740/LB
24,828 kWh
Lifetime gap
5,707 kWh
Output when it is hot
Rated power carried across the range a module actually sees
Scenario
JAM78S30-590/MR
JAM66D46-740/LB
Standard test conditions
25 °C
100.0% of rated power
590 W
740 W
Cool, bright day
40 °C
94.8% of rated power
559 W
708 W
Typical summer roof
55 °C
89.5% of rated power
528 W
676 W
Hot roof
70 °C
84.2% of rated power
497 W
643 W
03
Full specification
Parameter
JAM78S30-590/MR
JAM66D46-740/LB
Difference
Power and efficiency
Rated power
590 Wp
740 Wp
+150 W for JAM66D46-740/LB
Module efficiency
21.10 %
23.80 %
+2.70 pp for JAM66D46-740/LB
Power density
211.1 Wp/m²
238.2 Wp/m²
+27.2 Wp/m² for JAM66D46-740/LB
Open-circuit voltage
53.30 V
49.80 V
3.50 V apart
Voltage at max power
44.80 V
41.96 V
2.84 V apart
Short-circuit current
13.93 A
18.73 A
4.80 A apart
Current at max power
13.17 A
17.64 A
4.47 A apart
Temperature
Temperature coefficient
-0.350 %/°C
-0.290 %/°C
+0.060 %/°C for JAM66D46-740/LB
Mechanical
Dimensions
2465x1134x35 mm
2384x1303x33 mm
2465x1134x35 mm vs 2384x1303x33 mm
Module area
2.795 m²
3.106 m²
0.311 m² apart
Weight
30.5 kg
38.2 kg
-7.7 kg for JAM78S30-590/MR
Weight per kWp
51.7 kg/kWp
51.6 kg/kWp
Effectively the same
Warranty and degradation
Product warranty
12 yrs
12 yrs
Same
Performance warranty
25 yrs
30 yrs
+5 yrs for JAM66D46-740/LB
Annual degradation
0.55 %/yr
0.40 %/yr
-0.15 %/yr for JAM66D46-740/LB
Technology
Cell technology
PERC
TOPCon
PERC vs TOPCon
Cell type
Monocrystalline
Monocrystalline
Same
Cell count
156
132
24 cells apart
Bifacial
No
Yes
No vs Yes
04
14,129 panels
Against the whole database
Efficiency
#9,365
vs
#462
JAM66D46-740/LB leads by 8,903 places
Power density
#9,360
vs
#460
JAM66D46-740/LB leads by 8,900 places
Heat behaviour
#10,489
vs
#2,220
JAM66D46-740/LB leads by 8,269 places
Weight
#5,108
vs
#5,026
JAM66D46-740/LB leads by 82 places
Warranty
#9,912
vs
#21
JAM66D46-740/LB leads by 9,891 places
Overall
#6,853
vs
#185
JAM66D46-740/LB leads by 6,668 places
05
Open the full database
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The same specification on paper
06
Written summary
Checking cache...
07
Questions about this pairing
Which panel is better: JA Solar JAM78S30-590/MR or JA Solar JAM66D46-740/LB?
According to our database: JA Solar JAM66D46-740/LB has higher module efficiency (23.80% vs 21.10%); JA Solar JAM66D46-740/LB tolerates heat better (temp coeff -0.290%/°C vs -0.350%/°C). See the full spec comparison and 30-year energy simulation above for a complete picture.
What is the efficiency of JA Solar JAM78S30-590/MR and JA Solar JAM66D46-740/LB?
JA Solar JAM78S30-590/MR has a module efficiency of 21.10%, while JA Solar JAM66D46-740/LB is 23.80%. Higher efficiency means more electricity from the same roof area - useful when space is limited.
What cell technology does JA Solar JAM78S30-590/MR use vs JA Solar JAM66D46-740/LB?
JA Solar JAM78S30-590/MR uses PERC cells; JA Solar JAM66D46-740/LB 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 JAM78S30-590/MR and JA Solar JAM66D46-740/LB?
JA Solar JAM78S30-590/MR has a 25 years power warranty; JA Solar JAM66D46-740/LB 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 JAM78S30-590/MR and JA Solar JAM66D46-740/LB bifacial panels?
JA Solar JAM66D46-740/LB is bifacial (captures light from both faces); JA Solar JAM78S30-590/MR is monofacial. Bifacial panels work best on ground mounts or raised structures with a light-coloured surface underneath.
Shop prices: See 318 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.