First Solar Series 6 Plus 465W vs Heliene 108M10 420W
The Heliene 108M10 420W wins this comparison by a decisive margin. It leads in efficiency (21.5% vs 19.2%) and matches or exceeds on warranty (25 vs 10 years). For most residential installations, the Heliene 108M10 420W is the stronger choice.
Key Differences
- • First Solar Series 6 Plus 465W is rated at 465W while Heliene 108M10 420W is rated at 420W, a 45W difference.
- • Heliene 108M10 420W achieves 21.5% efficiency vs 19.2% for the other, a 2.3 percentage point gap.
- • Heliene 108M10 420W comes with a 25-year product warranty vs 10 years for the other.
- • First Solar Series 6 Plus 465W has a superior temperature coefficient of -0.28%/°C vs -0.34%/°C, retaining more power in hot climates.
- • First Solar Series 6 Plus 465W uses CdTe (Cadmium Telluride) cells while Heliene 108M10 420W uses Mono PERC Half-cut cells, representing different technology generations.
Specifications Breakdown
Module Efficiency
The Heliene 108M10 420W achieves 21.5% module efficiency compared to First Solar Series 6 Plus 465W's 19.2%, meaning Heliene 108M10 420W converts 2.3 percentage points more sunlight into electricity per square meter. In practical terms, the First Solar Series 6 Plus 465W produces 187.9 watts per square meter of panel area while the Heliene 108M10 420W produces 215.1 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
The First Solar Series 6 Plus 465W delivers 465W per panel versus 420W for the Heliene 108M10 420W, a 45W difference per module. To build an 8 kW residential system, you would need 18 First Solar Series 6 Plus 465W panels or 20 Heliene 108M10 420W panels. Choosing the higher-wattage option saves 2 panels, reducing total racking hardware, wiring, and installation labor costs. Higher wattage per panel is particularly valuable for commercial-scale installations where panel count directly impacts balance-of-system costs.
Temperature Coefficient
The First Solar Series 6 Plus 465W has a temperature coefficient of -0.28%/°C versus -0.34%/°C for the Heliene 108M10 420W. On a hot summer day when cell temperature reaches 65°C (40°C above the 25°C STC baseline), the First Solar Series 6 Plus 465W retains 94.4% of its rated power while the other retains 93.2%. This difference is particularly significant in hot climates such as the American Southwest, the Middle East, and Southeast Asia, where panels routinely operate 30-40°C above STC for several hours each day. Over the system lifetime, the cumulative energy advantage from a better temperature coefficient can amount to 2-4% of total production.
Warranty Coverage
The First Solar Series 6 Plus 465W is backed by a 10-year product warranty and 30-year performance guarantee, while the Heliene 108M10 420W offers 25-year product and 25-year performance coverage. The Heliene 108M10 420W provides 15 additional years of defect protection, covering manufacturing issues, material failures, and premature performance loss. Based on their published degradation rates (1.5% first year then 0.5%/year for First Solar Series 6 Plus 465W; 1.5% first year then 0.5%/year for Heliene 108M10 420W), after 25 years the First Solar Series 6 Plus 465W should retain approximately 86.5% of original output versus 86.5% for the Heliene 108M10 420W. The end-of-life output levels are closely matched.
Physical Dimensions & Weight
The First Solar Series 6 Plus 465W measures 2009×1232×49mm and weighs 34.5 kg, while the Heliene 108M10 420W measures 1722×1134×30mm at 21.5 kg. 2.48 m² of panel area for the First Solar Series 6 Plus 465W versus 1.95 m² for the Heliene 108M10 420W. The Heliene 108M10 420W is 13.0 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 260 kg. The more compact Heliene 108M10 420W may be easier to fit on irregularly shaped or space-limited rooftops.
Specification Comparison
| Specification | First Solar Series 6 Plus 465W | Heliene 108M10 420W |
|---|---|---|
| Power | 465W | 420W |
| Efficiency | 19.2% | 21.5% |
| Power Density | 17.5 W/sq ft | 20.0 W/sq ft |
| Cell Type | CdTe (Cadmium Telluride) | Mono PERC Half-cut |
| Bifacial | No | No |
| Weight | 34.5 kg | 21.5 kg |
| Temp Coefficient | -0.28%/°C | -0.34%/°C |
| Snow Load | 5400 Pa | 5400 Pa |
| Wind Load | 4000 Pa | 2400 Pa |
| Product Warranty | 10 years | 25 years |
| Performance Warranty | 30 years | 25 years |
| Degradation (Year 1) | 1.5% | 1.5% |
| Annual Degradation | 0.5% | 0.5% |
| Country | United States | Canada |
5-Dimension Head-to-Head Analysis
1. Efficiency & Power Density
Winner: Heliene 108M10 420WThe Heliene 108M10 420W achieves 21.5% efficiency versus 19.2% — a 2.3 percentage point advantage. On a typical 30-panel residential roof, this translates to approximately 1.4 kW more total system capacity, or 7 kWh more annual production in an average US location.
2. Hot Climate Performance
Winner: First Solar Series 6 Plus 465WThe First Solar Series 6 Plus 465W has a better temperature coefficient of -0.28%/°C versus -0.34%/°C. On a 45°C summer day (20°C above STC), the winner retains 94.4% of rated power versus 93.2%. This is a meaningful difference in hot states like Arizona, Texas, and Florida.
3. Durability & Warranty
Winner: Heliene 108M10 420WHeliene 108M10 420W leads with a 25-year product warranty versus 10 years. After 25 years, expect 86.5% vs 86.5% of original output for First Solar Series 6 Plus 465W and Heliene 108M10 420W respectively.
4. Power Output
Winner: First Solar Series 6 Plus 465WThe First Solar Series 6 Plus 465W delivers 465W versus 420W per panel — 45W more. For an 8 kW system, you need 18 panels with the higher-wattage option versus 20 panels, saving 2 panels and the associated racking and labor costs.
5. Cell Technology
Winner: First Solar Series 6 Plus 465WThe First Solar Series 6 Plus 465W uses CdTe (Cadmium Telluride): CdTe (Cadmium Telluride). The Heliene 108M10 420W uses Mono PERC Half-cut: PERC (Passivated Emitter Rear Cell) is the current mainstream technology, offering good efficiency at the lowest manufacturing cost. CdTe (Cadmium Telluride) represents a newer generation technology with a longer performance runway as manufacturing matures.
First Solar Series 6 Plus 465W
The Series 6 Plus delivers 465W using First Solar's proven CdTe thin-film technology, manufactured in the United States.
Pros
- + Proven US thin-film technology
- + Excellent temperature coefficient
- + Environmentally responsible
- + Strong bankability
Cons
- - Lower efficiency
- - Very heavy panel
- - Not suitable for residential
Heliene 108M10 420W
The Heliene 108M10 420W is a standard residential-format mono PERC panel manufactured in Heliene's North American facilities (Ontario, Canada and Mountain Iron, Minnesota). The 108 half-cut cell design in the standard 1722 x 1134mm format ensures universal racking compatibility. As one of the few PERC panels made in North America, it offers domestic content ITC bonus eligibility at a more accessible price point than Heliene's HJT line. Backed by Heliene's 25-year product warranty and accessible Canadian/US-based support.
Pros
- + North American manufactured — domestic content ITC bonus eligible
- + Standard 108-cell residential format fits all racking systems
- + More affordable than HJT panels while qualifying for domestic content bonus
- + 25-year product and performance warranties
- + Canadian and US-based customer support
- + 420W competitive output for standard residential size
Cons
- - PERC technology — less efficient than TOPCon/HJT in hot climates
- - -0.34%/°C temp coefficient is standard, not exceptional
- - 420W is competitive but not class-leading
- - Higher cost than Chinese-made PERC panels of similar specs
Choose First Solar Series 6 Plus 465W If...
- ✓ You want fewer panels to reach your target system size, reducing racking and labor costs
- ✓ You live in a hot climate (Arizona, Texas, Florida) where heat performance matters
- ✓ Large commercial and utility projects wanting proven US thin-film technology.
Choose Heliene 108M10 420W If...
- ✓ Your roof space is limited and you need maximum power per panel
- ✓ Long-term warranty protection is a top priority and you plan to stay in your home for 25+ years
- ✓ Budget-conscious homeowners who want North American-made panels for domestic content ITC bonus without paying the HJT premium.
Our Recommendation
The Heliene 108M10 420W is the decisive winner in this solar panel comparison, outperforming the First Solar Series 6 Plus 465W in 2 of 5 dimensions. Unless you have a specific requirement that the First Solar Series 6 Plus 465W uniquely addresses, the Heliene 108M10 420W is the stronger choice for virtually every installation scenario.
Frequently Asked Questions
Which is better, First Solar Series 6 Plus 465W or Heliene 108M10 420W?
The Heliene 108M10 420W wins this comparison by a decisive margin. It leads in efficiency (21.5% vs 19.2%) and matches or exceeds on warranty (25 vs 10 years). For most residential installations, the Heliene 108M10 420W is the stronger choice.
Which panel is more efficient, First Solar Series 6 Plus 465W or Heliene 108M10 420W?
The Heliene 108M10 420W at 21.5% module efficiency. Higher efficiency means more watts per square foot of roof space, which is critical for space-constrained installations. The difference of 2.3 percentage points translates to approximately 45W per panel under standard test conditions.
Which has a better warranty, First Solar Series 6 Plus 465W or Heliene 108M10 420W?
The First Solar Series 6 Plus 465W comes with a 10-year product warranty and 30-year performance guarantee. The Heliene 108M10 420W offers 25-year product and 25-year performance warranties. Heliene 108M10 420W provides 15 additional years of product coverage.
Which panel performs better in hot weather?
The First Solar Series 6 Plus 465W has a temperature coefficient of -0.28%/°C and the Heliene 108M10 420W is -0.34%/°C. First Solar Series 6 Plus 465W retains more power in heat — important in states like Arizona, Texas, and Florida. A lower (less negative) temperature coefficient is better.
How many First Solar Series 6 Plus 465W vs Heliene 108M10 420W panels do I need for an 8 kW system?
For an 8 kW system: you need 18 First Solar Series 6 Plus 465W panels (465W each) or 20 Heliene 108M10 420W panels (420W each). The First Solar Series 6 Plus 465W requires fewer panels, saving on racking hardware and installation labor.
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Last updated: February 2026