How to Choose Solar Panels — 7 Key Factors to Consider

Introduction

With hundreds of solar panel brands and models on the market, choosing the right one can feel overwhelming. This guide breaks down the seven most important factors to evaluate when selecting solar panels for any project — from a small residential rooftop to a large commercial installation.

1. Cell Technology

The type of solar cell determines the panel's efficiency, temperature performance, and longevity.

• Mono PERC (P-type): Mature, cost-effective technology. Efficiency: 20–21.8%. Example: LONGi Hi-MO 6.
• N-type TOPCon: Next-generation technology with higher efficiency and lower degradation. Efficiency: 21.5–22.8%. Example: LONGi Hi-MO 7.
• HJT: Premium technology with the best temperature coefficient. Efficiency: 21.5–22.5%. Higher cost.

For most projects in 2026, N-type TOPCon offers the best balance of performance, availability, and value.

2. Efficiency Rating

Higher efficiency means more power from less roof space. In 2026, look for panels above 21% efficiency for residential and above 22% for commercial projects. LONGi Hi-MO 7 achieves 22.8%, among the industry's highest.

3. Temperature Coefficient

Critical for hot climates. The temperature coefficient tells you how much power drops per degree above 25°C. Lower values are better:

• Mono PERC: −0.34 to −0.38%/°C
• N-type TOPCon: −0.29 to −0.32%/°C
• HJT: −0.24 to −0.26%/°C

4. Warranty Terms

Look for two separate warranties:

• Product warranty: Covers manufacturing defects. Look for 25 years minimum.
• Performance warranty: Guarantees minimum output over time. Look for 87.4%+ at year 25 or 30.

LONGi offers 25-year product and 30-year performance warranties on Hi-MO 7 panels.

5. Manufacturer Bankability

Choose a Tier 1 manufacturer (rated by BloombergNEF) to ensure long-term warranty support. LONGi is the world's largest solar panel manufacturer with a strong Tier 1 rating and global manufacturing capacity exceeding 100 GW.

6. Certifications

Essential certifications include:

• IEC 61215: Design qualification and type approval
• IEC 61730: Safety qualification
• IEC 61701: Salt mist corrosion (important for coastal areas)
• IEC 62716: Ammonia corrosion (for agricultural settings)
• UL 1703 / UL 61730: North American safety standards

7. Price vs Value

The cheapest panel is rarely the best value. Calculate the levelised cost of energy (LCOE) over 25–30 years. A panel costing 10% more but producing 5% more energy and degrading 0.1% less per year will deliver better lifetime value.

Decision Matrix

Priority	Best Choice	LONGi Option
Maximum efficiency	N-type TOPCon	Hi-MO 7 (22.8%)
Hot climate performance	N-type TOPCon or HJT	Hi-MO 7 (−0.29%/°C)
Best value	Mono PERC	Hi-MO 6
Ground-mount utility	Bifacial N-type	Hi-MO X6
Longest warranty	N-type TOPCon	Hi-MO 7 (30-year performance)

Frequently Asked Questions

What is the most important factor when choosing solar panels?

Efficiency and temperature coefficient are the most important for energy production. However, manufacturer bankability and warranty terms are equally critical for long-term peace of mind.

Should I choose the cheapest solar panel?

No. The cheapest panel often has lower efficiency, higher degradation, and shorter warranties. Calculate the LCOE over 25–30 years for a true cost comparison.

Is LONGi a good solar panel brand?

Yes. LONGi is the world's largest solar manufacturer, a consistent Tier 1 rated company, and a technology leader with multiple world efficiency records. Their Hi-MO series is used in major projects worldwide.