What Are the Different Types of Solar Cables?
The three main types of solar power cables are PV Wire, USE-2 Wire, and THHN Wire — each designed for specific roles within a photovoltaic (PV) system.
Solar panels are just one part of a complete photovoltaic (PV) system. Behind the scenes, specialized cables transmit energy from panels to inverters and grids. Choosing the right solar cable is essential for system safety, durability, and compliance.
- PV Wire (Photovoltaic Wire)
- USE-2 Wire (Underground Service Entrance, Type 2)
- THHN Wire (Thermoplastic High Heat-resistant Nylon-coated)
Each type offers different insulation, voltage ratings, and environmental protections. Here’s a breakdown of their core specs:
| Conductor | Insulation | Voltage Rating | Max. Temperature | UL Styles |
|---|---|---|---|---|
| Bare or Tinned Copper | XLPE | 600V, 1000V, or 2000V | 105°C Dry, 90°C Wet | UL44, UL4703 |
| Aluminum, Bare or Tinned Copper | XLPE | 600V | 90°C Dry and Wet | UL44, UL854 |
| Bare Copper | PVC | 600V | 90°C Dry, 75°C Wet | UL83, UL1063 |
All three wire types are available in RoHS-compliant versions (free of hazardous substances), aligning with green energy goals.
What Is PV Wire?
PV Wire is a solar power cable used for interconnection wiring in photovoltaic systems, featuring XLPE insulation and rated for harsh outdoor conditions.
Solar Panel PV Wire is a very popular cable used for interconnection wiring in photovoltaic (PV) systems. Most PV Wire features XLPE insulation and either bare or tinned copper conductors. This XLPE insulation makes the wire ozone, UV, sunlight, and moisture resistant, allowing it to withstand the environmental demands of solar power applications.
Key performance specs:
- Maximum Temperature: +90°C in wet environments, +150°C in dry environments
- Voltage Ratings: 600V, 1000V, or 2000V
- Applications: Interconnection wiring, underground service entrance, direct burial
- Suitable for: Grounded and ungrounded PV arrays
- Standards: UL 4703
PV Wire is extremely durable and built specifically for the rigorous environmental conditions found in solar power applications. Its thick insulation also makes it appropriate for direct burial installations.
What Is USE-2 Wire?
USE-2 Wire is a solar cable designed for underground service in grounded PV systems, offering high impact, oil, and moisture resistance.
USE-2 Wire (Underground Service Entrance, Type 2) is used primarily in grounded PV systems, particularly where the wire will be exposed to dirt, moisture, or physical stress. It features XLPE insulation and is available with aluminum, bare copper, or tinned copper conductors.
This cable is often dual-rated as RHH/RHW — meaning it combines the high heat resistance of RHH wire with the moisture resistance of RHW wire.
Key Specs & Features:
- Insulation: XLPE
- Conductor Options: Aluminum, Bare Copper, or Tinned Copper
- Voltage Rating: 600V
- Temperature Rating: 90°C (wet and dry)
- Standards: UL 854, UL 44
- Dual Rated: Often RHH/RHW for heat and water protection
- Resistance: Crush, oil, gas, and impact
Because of its ruggedness and insulation, USE-2 Wire is ideal for industrial solar applications where grounded arrays and underground runs are common.
Compared to PV Wire, USE-2 has:
- Thinner insulation and jacket
- Less resistance to sunlight and flame
- Reduced flexibility in cold temperatures
For ungrounded PV arrays or harsh environments, PV Wire remains the better option.
What Is THHN Wire?
THHN Wire is a building wire used in power applications that may appear in solar systems, but it is not suitable for conditions requiring USE-2 or PV Wire.
THHN wire is also commonly used in solar applications. It is a building wire used to carry electrical currents through power systems. Like USE-2 wire, THHN has a voltage rating of 600V and a maximum temperature of +90°C in dry locations.
However, THHN wire has only a maximum temperature rating of +75°C in wet environments. For this reason, it should never be used in solar applications that specifically call for USE-2 or PV Wire.
Why THHN is not a substitute:
- It does not meet the same strength or environmental resistance standards
- It lacks the specialized construction of PV and USE-2 Wire
- It is not rated for severe environmental conditions found in many solar installs
If a standard or specification explicitly requires USE-2 or PV Wire, THHN wire must not be used. While it serves similar electrical functions, its construction makes it unsuitable for harsh solar applications. Using THHN in these conditions may lead to system failure.
Which Solar Wire Should You Choose?
Each solar wire type—PV Wire, USE-2 Wire, and THHN—serves different roles. Choosing the right one depends on system design, code compliance, and environmental factors.
All solar cables play critical roles in:
- Solar generators
- Charge controllers
- Service grid tie-ins
Choosing the correct type ensures:
- Electrical safety
- Long-term system performance
- Regulatory compliance (UL, RoHS)
RoHS-compliant options are available for all three, making your system cleaner and more sustainable.
Trusted Source for Solar Cables
Allied Wire & Cable offers a full line of PV Wire, USE-2 Wire, and THHN Wire designed to meet strict solar application standards. All products are UL-rated and RoHS-compliant. Get the durability and code compliance you need — backed by expert support.
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