LONGi Hi-MO 7 590W vs JA Solar JAM78S30 590W
The JA Solar JAM78S30 590W wins this comparison by a clear margin. It offers better long-term durability with 15-year warranty. For most residential installations, the JA Solar JAM78S30 590W is the stronger choice.
Key Differences
- • Both panels are rated at 590W, so the comparison comes down to efficiency, warranty, and technology.
- • LONGi Hi-MO 7 590W achieves 22.8% efficiency vs 22.6% for the other, a 0.2 percentage point gap.
- • JA Solar JAM78S30 590W comes with a 15-year product warranty vs 12 years for the other.
- • LONGi Hi-MO 7 590W uses HPBC (Back Contact N-type) cells while JA Solar JAM78S30 590W uses TOPCon N-type cells, representing different technology generations.
Specifications Breakdown
Module Efficiency
The LONGi Hi-MO 7 590W achieves 22.8% module efficiency compared to JA Solar JAM78S30 590W's 22.6%, meaning LONGi Hi-MO 7 590W converts 0.2 percentage points more sunlight into electricity per square meter. In practical terms, the LONGi Hi-MO 7 590W produces 228.4 watts per square meter of panel area while the JA Solar JAM78S30 590W produces 218.2 W/m². For rooftop installations where space is limited, this efficiency gap determines how many kilowatts you can fit on your available roof area. Over a 25-year system life, even a small efficiency advantage compounds into meaningful additional energy production.
Power Output
Both panels are rated at 590W under standard test conditions (STC), requiring 14 panels each to build an 8 kW system. With identical wattage ratings, the power output dimension is a draw and does not favor either panel. The real differentiators become efficiency density, temperature behavior, and long-term degradation rates which determine actual field performance beyond the nameplate rating.
Temperature Coefficient
Both panels share an identical temperature coefficient of -0.28%/°C, meaning they lose power at the same rate as cell temperature rises above the 25°C standard test baseline. At 65°C cell temperature, both retain 94.4% of rated power. Neither panel has a thermal performance advantage, which makes this specification a non-factor in the comparison.
Warranty Coverage
The LONGi Hi-MO 7 590W is backed by a 12-year product warranty and 30-year performance guarantee, while the JA Solar JAM78S30 590W offers 15-year product and 30-year performance coverage. The JA Solar JAM78S30 590W provides 3 additional years of defect protection, covering manufacturing issues, material failures, and premature performance loss. Based on their published degradation rates (1% first year then 0.4%/year for LONGi Hi-MO 7 590W; 1% first year then 0.4%/year for JA Solar JAM78S30 590W), after 25 years the LONGi Hi-MO 7 590W should retain approximately 89.4% of original output versus 89.4% for the JA Solar JAM78S30 590W. The end-of-life output levels are closely matched.
Physical Dimensions & Weight
The LONGi Hi-MO 7 590W measures 2278×1134×35mm and weighs 28.8 kg, while the JA Solar JAM78S30 590W measures 2384×1134×35mm at 31 kg. 2.58 m² of panel area for the LONGi Hi-MO 7 590W versus 2.70 m² for the JA Solar JAM78S30 590W. The LONGi Hi-MO 7 590W is 2.2 kg lighter per panel, which reduces structural load requirements on the roof and makes handling easier during installation. For a 20-panel system, that is a total weight difference of 44 kg. The more compact LONGi Hi-MO 7 590W may be easier to fit on irregularly shaped or space-limited rooftops.
Specification Comparison
| Specification | LONGi Hi-MO 7 590W | JA Solar JAM78S30 590W |
|---|---|---|
| Power | 590W | 590W |
| Efficiency | 22.8% | 22.6% |
| Power Density | 21.2 W/sq ft | 20.3 W/sq ft |
| Cell Type | HPBC (Back Contact N-type) | TOPCon N-type |
| Bifacial | Yes | No |
| Weight | 28.8 kg | 31 kg |
| Temp Coefficient | -0.28%/°C | -0.28%/°C |
| Snow Load | 5400 Pa | 5400 Pa |
| Wind Load | 2400 Pa | 2400 Pa |
| Product Warranty | 12 years | 15 years |
| Performance Warranty | 30 years | 30 years |
| Degradation (Year 1) | 1% | 1% |
| Annual Degradation | 0.4% | 0.4% |
| Country | China | China |
5-Dimension Head-to-Head Analysis
1. Efficiency & Power Density
Winner: LONGi Hi-MO 7 590WThe LONGi Hi-MO 7 590W achieves 22.8% efficiency versus 22.6% — a 0.2 percentage point advantage. On a typical 30-panel residential roof, this translates to approximately 0.0 kW more total system capacity, or 0 kWh more annual production in an average US location.
2. Hot Climate Performance
Winner: TieBoth panels share a temperature coefficient of -0.28%/°C — identical heat tolerance.
3. Durability & Warranty
Winner: JA Solar JAM78S30 590WJA Solar JAM78S30 590W leads with a 15-year product warranty versus 12 years. After 25 years, expect 89.4% vs 89.4% of original output for LONGi Hi-MO 7 590W and JA Solar JAM78S30 590W respectively.
4. Power Output
Winner: TieBoth panels deliver 590W — identical power output per panel. System cost per watt will be the deciding factor.
5. Cell Technology
Winner: LONGi Hi-MO 7 590WThe LONGi Hi-MO 7 590W uses HPBC (Back Contact N-type): HPBC (Hybrid Passivated Back Contact) is a proprietary LONGi architecture combining back-contact design with advanced passivation for both high efficiency and aesthetic uniformity. The JA Solar JAM78S30 590W uses TOPCon N-type: TOPCon (Tunnel Oxide Passivated Contact) adds a thin tunnel oxide layer to reduce recombination losses, achieving higher efficiency than PERC while being manufacturable on existing production lines. HPBC (Back Contact N-type) represents a newer generation technology with a longer performance runway as manufacturing matures.
LONGi Hi-MO 7 590W
The Hi-MO 7 is LONGi's flagship residential panel using proprietary HPBC (Hybrid Passivated Back Contact) cell technology for exceptional 22.8% efficiency and 590W output.
Pros
- + Industry-leading HPBC back-contact technology
- + 22.8% efficiency
- + Excellent temperature coefficient
- + Lower degradation rate
Cons
- - Premium pricing
- - Heavy at 28.8 kg
- - New technology with limited track record
JA Solar JAM78S30 590W
JA Solar's JAM78S30 is a high-wattage N-type TOPCon module achieving 22.6% efficiency for large-scale installations.
Pros
- + Very high 590W output
- + Excellent efficiency
- + Low temperature coefficient
- + Bifacial design
Cons
- - Very large and heavy
- - Requires heavy-duty mounting
- - Not for small roofs
Choose LONGi Hi-MO 7 590W If...
- ✓ Your roof space is limited and you need maximum power per panel
- ✓ Premium residential installations seeking maximum efficiency.
Choose JA Solar JAM78S30 590W If...
- ✓ Long-term warranty protection is a top priority and you plan to stay in your home for 15+ years
- ✓ You prefer newer cell technology with a longer performance improvement runway
- ✓ Large commercial or ground-mount systems requiring maximum output.
Our Recommendation
We recommend the JA Solar JAM78S30 590W for most buyers in this comparison. It wins 1 of 5 key dimensions and offers a clear advantage in the metrics that matter most for a solar panel purchase. The LONGi Hi-MO 7 590W remains a good product, but the JA Solar JAM78S30 590W delivers better overall value for the majority of installations.
Frequently Asked Questions
Which is better, LONGi Hi-MO 7 590W or JA Solar JAM78S30 590W?
The JA Solar JAM78S30 590W wins this comparison by a clear margin. It offers better long-term durability with 15-year warranty. For most residential installations, the JA Solar JAM78S30 590W is the stronger choice.
Which panel is more efficient, LONGi Hi-MO 7 590W or JA Solar JAM78S30 590W?
The LONGi Hi-MO 7 590W at 22.8% module efficiency. Higher efficiency means more watts per square foot of roof space, which is critical for space-constrained installations. The difference of 0.2 percentage points translates to approximately 0W per panel under standard test conditions.
Which has a better warranty, LONGi Hi-MO 7 590W or JA Solar JAM78S30 590W?
The LONGi Hi-MO 7 590W comes with a 12-year product warranty and 30-year performance guarantee. The JA Solar JAM78S30 590W offers 15-year product and 30-year performance warranties. JA Solar JAM78S30 590W provides 3 additional years of product coverage.
Which panel performs better in hot weather?
The LONGi Hi-MO 7 590W has a temperature coefficient of -0.28%/°C and the JA Solar JAM78S30 590W is -0.28%/°C. Both handle heat equally. A lower (less negative) temperature coefficient is better.
How many LONGi Hi-MO 7 590W vs JA Solar JAM78S30 590W panels do I need for an 8 kW system?
For an 8 kW system: you need 14 LONGi Hi-MO 7 590W panels (590W each) or 14 JA Solar JAM78S30 590W panels (590W each). Both require the same number of panels.
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Last updated: February 2026