Sizing Solar System Wires: Formulas and Guidelines

When setting up a solar system, correctly sizing wires is crucial for optimal performance and safety. Wires that are too small can lead to power losses and overheating, while oversized wires can increase costs unnecessarily. Here’s a guide on how to size solar system wires using the right formulas and guidelines.

Understanding Wire Sizing

The size of a wire is measured in square millimeters (mmΒ²) or circular mils (CM). The current-carrying capacity of a wire and its resistance are key factors in determining the wire size needed for a solar system.

Formulas for Sizing Wires

DC Wire Sizing: For DC circuits, you can use the following formula to calculate the wire size based on current (I) in amps and distance (D) in meters:

π‘Šπ‘–π‘Ÿπ‘’ 𝑆𝑖𝑧𝑒 (π‘šπ‘š2) = (1.25×𝐼×𝐷) Γ· π‘‰π‘œπ‘™π‘‘π‘Žπ‘”π‘’ π·π‘Ÿπ‘œπ‘ Wire Size(mm2) = (1.25Γ—IΓ—D) Γ· Voltage Drop

  • The factor 1.25 accounts for safety margins.
  • Voltage drop is typically limited to 2% for efficient systems.

    AC Wire Sizing: The formula for AC circuits depends on the current (I) in amps and the voltage (V) in volts:

    π‘Šπ‘–π‘Ÿπ‘’ 𝑆𝑖𝑧𝑒 (π‘šπ‘š2) = (2×𝐼×𝐷) Γ· π‘‰π‘œπ‘™π‘‘π‘Žπ‘”π‘’ π·π‘Ÿπ‘œπ‘ Wire Size(mm2) = (2Γ—IΓ—D) Γ· Voltage Drop

    • The factor 2 allows for both supply and return conductors in AC systems.
    • Again, keep the voltage drop within an acceptable range (e.g., 3% for AC).

      Guidelines for Wire Sizing

      • Consider Voltage Drop: Ensure that the voltage drop in your system is within acceptable limits. Use voltage drop calculators or tables to determine the maximum allowable drop.
      • Consult Standards: Refer to local electrical codes and standards for specific requirements regarding wire sizing and installation practices.
      • Temperature Considerations: Factor in the ambient temperature where the wires will be installed, as higher temperatures can affect wire capacity.
      • Future Expansion: Plan for potential system expansions or upgrades when sizing wires to avoid limitations in the future.


      Properly sizing wires for your solar system is crucial for safety, efficiency, and long-term performance. By understanding the formulas and guidelines outlined here, you can ensure that your solar installation meets the necessary electrical standards and functions optimally for years to come.

      For expert guidance and assistance with solar system installations, contact Immortals Solar today. Our team of professionals specializes in renewable energy solutions, making your investment in solar power both sustainable and rewarding.

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