JAM78S30-595/MR vs JAM66D46-740/LB 3 of 19 identical Swap Change panels

JA Solar JAM78S30-595/MR vs JA Solar JAM66D46-740/LB

Q: Which panel is better: JA Solar JAM78S30-595/MR or JA Solar JAM66D46-740/LB?

According to our database: JA Solar JAM66D46-740/LB has higher module efficiency (23.80% vs 21.30%); 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.

Q: What is the efficiency of JA Solar JAM78S30-595/MR and JA Solar JAM66D46-740/LB?

JA Solar JAM78S30-595/MR has a module efficiency of 21.30%, while JA Solar JAM66D46-740/LB is 23.80%. Higher efficiency means more electricity from the same roof area - useful when space is limited.

Q: What cell technology does JA Solar JAM78S30-595/MR use vs JA Solar JAM66D46-740/LB?

JA Solar JAM78S30-595/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.

Q: What is the warranty on JA Solar JAM78S30-595/MR and JA Solar JAM66D46-740/LB?

JA Solar JAM78S30-595/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.

Q: Are JA Solar JAM78S30-595/MR and JA Solar JAM66D46-740/LB bifacial panels?

JA Solar JAM66D46-740/LB is bifacial (captures light from both faces); JA Solar JAM78S30-595/MR is monofacial. Bifacial panels work best on ground mounts or raised structures with a light-coloured surface underneath.

JAM78S30-595/MR

595 Wp 21.30 % PERC

Open panel page Datasheet PDF

JAM66D46-740/LB

740 Wp 23.80 % TOPCon Bifacial

Open panel page Datasheet PDF

The verdict

JAM66D46-740/LB leads on the differences that matter

The largest is module efficiency: 2.50 pp more efficient. 3 of 19 comparable parameters are identical.

See all 16 differences

How alike are they

3 of 19 comparable
parameters are identical

identical differs

What actually differs

16 of 19 parameters

Parameter JAM78S30-595/MR JAM66D46-740/LB Difference

Module efficiency 21.30 % 23.80 % 2.50 pp more efficient

Temperature coefficient -0.350 %/°C -0.290 %/°C 0.060 %/°C better in heat

Rated power 595 Wp 740 Wp 145 W more power

Power density 212.9 Wp/m² 238.2 Wp/m² 25.4 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 13.98 A 18.73 A 4.75 A apart

Module area 2.795 m² 3.106 m² 0.311 m² apart

Open-circuit voltage 53.40 V 49.80 V 3.60 V apart

Cell technology PERC TOPCon PERC vs TOPCon

Current at max power 13.21 A 17.64 A 4.43 A apart

Cell count 156 132 24 cells apart

Voltage at max power 45.05 V 41.96 V 3.09 V apart

Bifacial No Yes No vs Yes

Dimensions 2465x1134x35 mm 2384x1303x33 mm 2465x1134x35 mm vs 2384x1303x33 mm

What it means on a roof

Thirty years of production

Each panel's own declared degradation curve, at 1,200 kWh/kWp a year

Cell temperature

JAM78S30-595/MR

19,283 kWh

JAM66D46-740/LB

24,828 kWh

Lifetime gap

5,545 kWh

Output when it is hot

Rated power carried across the range a module actually sees

Scenario JAM78S30-595/MR JAM66D46-740/LB

Standard test conditions 25 °C 100.0% of rated power 595 W 740 W

Cool, bright day 40 °C 94.8% of rated power 564 W 708 W

Typical summer roof 55 °C 89.5% of rated power 533 W 676 W

Hot roof 70 °C 84.2% of rated power 501 W 643 W

Full specification

Parameter JAM78S30-595/MR JAM66D46-740/LB Difference

Power and efficiency

Rated power 595 Wp 740 Wp +145 W for JAM66D46-740/LB

Module efficiency 21.30 % 23.80 % +2.50 pp for JAM66D46-740/LB

Power density 212.9 Wp/m² 238.2 Wp/m² +25.4 Wp/m² for JAM66D46-740/LB

Open-circuit voltage 53.40 V 49.80 V 3.60 V apart

Voltage at max power 45.05 V 41.96 V 3.09 V apart

Short-circuit current 13.98 A 18.73 A 4.75 A apart

Current at max power 13.21 A 17.64 A 4.43 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 JAM78S30-595/MR

Weight per kWp 51.3 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

Against the whole database

14,129 panels

Efficiency

#8,585 vs #462

JAM66D46-740/LB leads by 8,123 places

Power density

#8,667 vs #460

JAM66D46-740/LB leads by 8,207 places

Heat behaviour

#10,489 vs #2,220

JAM66D46-740/LB leads by 8,269 places

Weight

#4,683 vs #5,026

JAM78S30-595/MR leads by 343 places

Warranty

#9,912 vs #21

JAM66D46-740/LB leads by 9,891 places

Overall

#6,416 vs #185

JAM66D46-740/LB leads by 6,231 places

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The same specification on paper

Written summary

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Questions about this pairing

Which panel is better: JA Solar JAM78S30-595/MR or JA Solar JAM66D46-740/LB?

According to our database: JA Solar JAM66D46-740/LB has higher module efficiency (23.80% vs 21.30%); 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 JAM78S30-595/MR and JA Solar JAM66D46-740/LB?

JA Solar JAM78S30-595/MR has a module efficiency of 21.30%, 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 JAM78S30-595/MR use vs JA Solar JAM66D46-740/LB?

JA Solar JAM78S30-595/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 JAM78S30-595/MR and JA Solar JAM66D46-740/LB?

JA Solar JAM78S30-595/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 JAM78S30-595/MR and JA Solar JAM66D46-740/LB bifacial panels?

JA Solar JAM66D46-740/LB is bifacial (captures light from both faces); JA Solar JAM78S30-595/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.