What is UL 4703? The Standard for PV Wire

What is UL 4703?

UL 4703 is the primary safety standard from Underwriters Laboratories (UL) governing the construction and testing of single-conductor Photovoltaic (PV) Wire. These sunlight-resistant cables are rated for 600V, 1000V, or 2000V.  While standard building wire often fails under constant environmental stress, UL 4703 ensures that solar interconnection wiring can survive 25+ years of intense UV radiation, extreme thermal cycling, and heavy moisture.  Below are a few more details related to this UL listing.  

The Construction Essentials

To meet the UL 4703 standard, every component of the cable is engineered for outdoor reliability:

• Insulation: Uses high-performance XLPE (Cross-Linked Polyethylene). This thermoset material won't melt or deform under extreme heat and provides superior dielectric strength.

• Conductors: Available in stranded copper (for maximum conductivity and flexibility) or 8000-series aluminum alloy (to reduce weight and material costs on large-scale solar farms).

Example of PV Wire (UL4703) in both copper & aluminum

Why Engineers Specify UL 4703

A cable doesn't earn a UL 4703 listing just for being "tough"—it must pass a series of rigorous environmental hurdles:

• 720-Hour UV Resistance: The insulation must maintain its integrity after nearly a month of intense, accelerated UV and ozone exposure.

• -40°C Cold Impact Test: The wire is frozen to sub-zero temperatures and struck with a weight; it must not crack or shatter.

• Ungrounded Support: Unlike older USE-2 standards, UL 4703 is approved for both grounded and ungrounded PV arrays (NEC 690), making it the modern standard for utility-scale inverters.
  

Common Applicatioms

• Solar String Wiring: Interconnecting individual panels.

• Combiner Box Leads: Transitioning from PV wire to THHN/THWN-2 for long conduit runs to the inverter.

• Utility-Scale Farms: High-voltage (2000V) DC collection systems.

How Wire America Can Help

At Wire America, we specialize in professional-grade UL 4703 Photovoltaic (PV) Wire designed for the most demanding solar environments. We offer a full range of sizes to power everything from residential rooftops to utility-scale farms:

• String Wiring: High-flexibility 10 AWG and 12 AWG copper for panel interconnection.

• Feeder Power: Massive conductors ranging from 4/0 AWG, 500 MCM up to 1000 MCM in 8000-series Aluminum.

• High-Voltage Ready: Full stock of 2000V rated PV wire for modern, high-efficiency inverter systems.

Ready to start your solar project? Shop our Copper and Aluminum PV Wire Collection here.

Official Resource: Visit the UL Standards page for UL 4703

At Wire America, we believe in genuine conversation. You'll always talk with real people who understand that every project requires careful product selection. We're here to ensure you feel educated, confident, and great about your final purchase. Feel free to give us a call to discuss your project! You can reach us at: 833-268-8644

⚠️ Important Disclaimer: Safety and Compliance

Wire America provides this information as a guide only. Electrical installations must strictly adhere to the National Electrical Code (NEC) and all state, local, and jurisdictional requirements, which vary widely. Always consult a licensed electrician, electrical engineer, or the local inspecting authority before purchasing material or starting any electrical project. Wire America assumes no liability for the installation, use, or interpretation of these guides.