Which cable is best for a solar panel?

In a solar power system, the cable may seem like an inconspicuous connecting component, but it is actually crucial to the system's performance—it transmits the DC power generated by the photovoltaic panels, directly impacting power generation efficiency, operational safety, and lifespan.​
Industry data shows that improper selection of solar cables can have significant consequences: power generation loss can reach 5-15% (a 10kW home system could lose 500-1500 kWh annually, costing 250-750 yuan at 0.5 yuan/kWh); there is a risk of insulation aging and short-circuit fires.  Furthermore, poor-quality cables have a lifespan of only 3-5 years, far shorter than the 20-30 year design life of photovoltaic panels. Replacing them requires dismantling part of the array, and the repair cost can be 3-5 times the initial investment, also disrupting power generation revenue. Therefore, scientific selection is key to a successful solar project.​
Why Must Solar Panels Use Dedicated Cables? Can't We Use Ordinary Wires?​
Ordinary household wires or general-purpose industrial cables cannot meet the special requirements of solar systems. The core reasons lie in three key challenges:​
The "Weather Resistance Challenge" of Extreme Outdoor Environments​
Solar cables must be exposed to the elements for extended periods, facing multiple natural hazards:​
The operating environment of solar cables is complex and variable, with high demands on performance from UV radiation, temperature, and environmental corrosion. When rewriting, these points should be presented cohesively, retaining key data and comparisons. Solar cables must withstand harsh environments: Under direct UV radiation, the PVC insulation of ordinary cables will age, crack, and become brittle within 1-2 years.  Specialized solar cables, however, use UV-resistant insulation materials that can withstand UV exposure for over 25 years.  Regarding temperature, ordinary cables become brittle and prone to cracking at low temperatures (down to -40°C in northern winters) and soften and leak at high temperatures (up to 90°C on the surface of PV panels in southern summers, exceeding 100°C in extreme weather).  Specialized cables, however, can operate stably from -40°C to 90°C.  Furthermore, environmental factors such as rain, snow, dust, and coastal salt spray accelerate oxidation of conductors in ordinary cables, while specialized cables, with their multi-layer sealing and corrosion-resistant materials, effectively prevent such damage.
"Long-Life Requirements" to Match PV Modules:
 The design lifespan of PV modules is typically 20-30 years. Using ordinary cables (with a lifespan of 5-8 years) would require replacement every 8-10 years—for a 10kW residential system, each replacement involves dismantling the frame and panels, taking 3-5 days and resulting in 150-250 kWh of lost power generation, plus labor and material costs, totaling 3000-5000 yuan. Specialized solar cables, with a design lifespan of 25-30 years, match the module lifespan, eliminating the hassle of frequent repairs.
"Safety and Compliance" for High-Voltage DC Systems:
Solar systems typically use high-voltage DC power (600V-1500V), often installed on rooftops or in other areas with frequent human activity. Given the high voltage and the specific operating environment, the cables used must comply with international standards to ensure system safety and reliability. For example, standards such as IEC 62930 (International Electrotechnical Commission), UL 4703 (Underwriters Laboratories), and EN 50618 (European Standard) not only require cables to have excellent insulation properties (to prevent electrical leakage), but also mandate "flame retardancy, low smoke, and halogen-free" features—ordinary cables release toxic hydrogen chloride gas and thick black smoke when burning, while specialized cables have a smoke transmittance of ≥60% and do not release halogens, thus providing more time for fire rescue operations.  Furthermore, these standards require that specialized cables withstand bending and pulling during installation, as well as wind sway and bird pecking during long-term use, with mechanical strength far exceeding that of ordinary wires.
Main Types of Solar Cables：
PV1-F Cable: 
The "cost-effective choice" for residential and small commercial applications Core structure: Uses a single-core flexible copper conductor, with both insulation and sheath made of XLPO (cross-linked polyolefin) material; rated voltage up to 1000V DC, suitable for 3-50kW residential and small commercial systems. Its advantages are significant: XLPO material has strong weather resistance, stable performance from -40°C to 90°C, and good flexibility for complex rooftop wiring, resulting in efficient installation; mature technology with a failure rate of less than 0.5% after decades of market validation, and a price 15%-20% lower than high-end cables. Suitable for residential rooftop PV systems under 10kW and small commercial projects (such as convenience stores, office buildings) under 50kW.
H1Z2Z2-K Cable: The "Safe and Durable Choice" for Large Projects
The Z2Z2HD 1500V solar cable, where "Z2Z2" in its name stands for "dual flame-retardant, low-smoke, halogen-free," and "H" indicates high temperature resistance.  It typically uses copper conductors (aluminum conductors are also available for large projects), with an enhanced XLPO material for insulation and sheath. This cable has a maximum voltage rating of 1500V DC, suitable for large commercial and industrial systems and photovoltaic power plants of 50kW and above. It complies with IEC 62930 and EN 50618 standards, producing minimal and non-toxic smoke in a fire, with a temperature resistance of up to 125°C. Its mechanical strength is 30% higher than PV1-F, capable of withstanding compression and tension during ground installation and direct burial. The 1500V high-voltage design allows for longer string lengths, enabling 50% more modules to be connected in series compared to a 1000V system, reducing the number of junction boxes and cable circuits, and lowering BOS (Balance of System) costs by 15-20%.  Its 30-year lifespan perfectly matches the operating cycle of a photovoltaic power plant, making it suitable for industrial photovoltaic systems of 100kW and above, and MW-scale photovoltaic power plants (such as a 10MW ground-mounted plant).
USE-2 Cable: "Compliance Essential" for the North American Market
When selecting solar cables for photovoltaic projects in North America, the key standard is UL 4703 certification, the "entry requirement" for such projects in the region. This cable offers significant performance advantages, with options for copper or aluminum conductors, an XLPE (cross-linked polyethylene) insulation layer, and a UV-resistant polymer sheath, providing excellent resistance to sunlight and moisture.  It supports direct burial installation (≥0.7m depth, no additional conduit required), effectively resisting mechanical damage and animal damage.  It also maintains flexibility at temperatures below -30°C, making it ideal for the harsh cold climates of northern North America. Voltage ratings range from 600V to 1000V DC, suitable for residential and commercial solar photovoltaic projects in North America, such as the United States and Canada, especially for ground-mounted systems requiring direct burial installation.
RHW/RHW-2 Cable: “A versatile cable for various applications” Key features:
The insulation uses XLPE material, offering excellent moisture resistance and high-temperature performance (RHW-2 withstands temperatures up to 90℃, 10℃ higher than RHW). Voltage ratings range from 600V to 1000V DC. Advantages: Besides its good conductivity and corrosion resistance, suitable for connecting modules and junction boxes, it can also serve as a grounding cable, effectively discharging lightning currents and protecting equipment.  It is also more cost-competitive, 10%-15% lower than USE-2, and widely available globally. Applications: Particularly suitable for photovoltaic systems in humid and high-temperature areas (such as rainy southern provinces), and can also be used as a grounding cable for various photovoltaic projects.
Special-purpose cables: Addressing specific installation challenges
Twin-core solar cable: Encasing two conductors in a single sheath reduces installation time by 50% and prevents cable damage, suitable for residential flat-roof solar systems with small module spacing (≤0.5m) and dense wiring. Aluminum-core solar cable: Made of high-purity aluminum (≥99.7%), 30%-40% lighter and 40%-50% cheaper than copper-core cables. By increasing the wire diameter, line loss can be comparable to copper-core cables, suitable for long-distance power transmission (1-2 km) in large-scale (>100MW) photovoltaic power plants, saving 5000-8000 RMB per kilometer in material and transportation costs.
Key Technical Parameters to Consider When Selecting Cables: One Wrong Choice Could Lead to Problems
After determining the cable type, you need to further refine the technical parameters. The following 4 indicators directly determine the cable's suitability and safety:
Conductor Material: Balancing "Conductivity, Corrosion Resistance, and Cost"
Tin-plated copper: Tin-plated on pure copper, isolating it from air and moisture, offering 3 times higher corrosion resistance than bare copper, especially suitable for coastal areas with high salt spray; 100% IACS conductivity (International Annealed Copper Standard), low line loss, good flexibility, suitable for complex rooftop installations; disadvantage: 10-15% higher cost than bare copper, recommended for residential and commercial projects in coastal areas;
Bare copper: Pure copper conductor, conductivity similar to tin-plated copper, lower cost, suitable for dry inland areas (e.g., Northwest and North China with low rainfall); disadvantage: prone to oxidation and formation of copper oxide in humid environments, increasing resistance, not recommended for coastal areas;
Aluminum: High-purity aluminum conductor, lightweight and low-cost, suitable for long-distance power transmission in large power plants; disadvantages: poor flexibility (bending radius ≥ 10 times diameter, otherwise prone to breakage), and requires special copper-aluminum transition connectors when connecting with copper (to prevent electrochemical corrosion), recommended for ground-mounted power plants over 100MW.
Insulation and Sheath Material: The "First Line of Defense" for Lifespan and Safety
XLPO (Cross-linked Polyolefin): Current mainstream choice, forming a three-dimensional network structure through cross-linking, resistant to UV, high and low temperatures (-40°C to 125°C), and chemical corrosion; halogen-free and low smoke when burning; lifespan of 25-30 years, suitable for all types of photovoltaic applications, an "all-purpose material" for residential, commercial, and power plant projects;
XLPE (Cross-linked Polyethylene): Similar performance to XLPO, slightly lower temperature resistance (-40°C to 90°C), slightly poorer flexibility, but 5-10% lower cost, suitable for dry inland areas or as grounding cables;
PVC (Polyvinyl Chloride): Absolutely DO NOT USE! Poor UV resistance (aging within 1-2 years), narrow temperature tolerance (-15°C to 60°C), and release of toxic hydrogen chloride during combustion, resulting in a lifespan of only 5-8 years—PVC cables are completely unsuitable for photovoltaic applications. Low-cost PVC cables on the market should be firmly rejected.
Voltage Rating: 
Must be precisely matched to the system voltage. The cable's rated voltage must be ≥ the system's maximum open-circuit voltage; otherwise, insulation breakdown and short circuits may occur. 600V DC: Only used for early small off-grid systems (below 3kW), now gradually phased out, only used in retrofits of older systems. 1000V DC: The mainstream choice, suitable for 3-50kW residential and small commercial systems (e.g., a 10kW residential system with 36 330W panels in series, open-circuit voltage of about 1000V). 1500V DC: The preferred choice for large projects, suitable for commercial, industrial systems, and power plants over 50kW. It reduces the number of junction boxes and cables, lowering BOS costs, and is the future trend for large-scale PV. Note: Allow for a 10-20% margin. If the system's maximum open-circuit voltage is 1000V, a 1200V DC cable should be selected (to avoid voltage fluctuations due to temperature rise and module aging).
Cross-sectional Area (Wire Gauge): Avoiding "Excessive Power Loss" and "Overheating/Fire Hazards"
Wire gauge is determined by the current load and transmission distance. An undersized wire will lead to high power loss and overheating, while an oversized wire wastes cost. Common sizing recommendations:
Residential systems (3-10kW): For distances ≤10 meters from the panels to the inverter, use 4mm²; for 10-20 meters, use 6mm²; for over 20 meters, use 10mm².
Commercial systems (50-100kW): For distances ≤50 meters, use 10mm²; for 50-100 meters, use 16mm².
Power plant systems (100MW and above): For 1-2 km distances from the array to the inverter room, use 25mm²-35mm² aluminum core (16mm²-25mm² copper core).
Calculation method: Power loss should be kept below 2%. It can be calculated using the formula "Power Loss Rate = (Current² × Resistance × Distance × 2) / Power", or by referring to the "Current Capacity - Distance Chart" provided by the cable manufacturer.
Conclusion
Selecting solar power cables should not solely focus on the "highest-end" product; rather, it should be based on the actual project requirements, finding a balance between efficiency, safety, and cost.
When selecting solar power cables, multiple factors should be considered:  For residential applications, cost-effective PV1-F cables are recommended; for commercial/industrial applications, the 1500V high-voltage H1Z2Z2-K cable is suitable to reduce BOS costs; for power plants, the H1Z2Z2-K aluminum-core cable can be used for long-distance power transmission to lower costs.  Regarding location, tin-plated copper conductors are recommended for coastal areas to resist salt spray, while low-temperature resistant cables (such as USE-2, which remains flexible at -30°C) are needed for cold regions. North American projects require UL-certified USE-2/RHW-2 cables to comply with NEC standards.  For safety, low-smoke, halogen-free H1Z2Z2-K cables effectively reduce fire risks in high-density areas like rooftops and factories.  Regarding lifespan, all projects should ensure a cable lifespan of ≥25 years to prevent premature failure and system downtime.