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Photovoltaics • DC • Cable

Calculate PV DC Cable Cross-Section

Calculate the required DC cable cross-section for PV cables based on current, length and voltage drop.

Calculation Values

PV cables are mostly copper

Note: This calculator provides a technical estimate for guidance only. For electrical installations, standards, protective measures, installation method, ambient temperature, grouping, protective devices and manufacturer specifications must also be checked.

Formula Used

A = (2 × L × I) / (κ × ΔU)

ΔU = U × voltage drop% ÷ 100

For DC, the positive and negative conductors are accounted for with a factor of 2.

Frequently Asked Questions

Why the factor 2 for DC?

The current flows through both the positive and negative conductor. That's why the one-way length is calculated with both the outgoing and return conductor accounted for.

What voltage drop is reasonable?

For PV DC cables, low voltage drop values are often targeted, for example around 1 percent.

Can I use this calculator for real PV planning?

It serves as a guideline. PV standards, protection concept, temperature, installation and manufacturer specifications must be checked.

Practical guidance

Check PV string cable size for DC voltage drop

String current flows between array and inverter; factor 2 includes positive and negative conductor paths.

Input values explained

Current
Enter the expected operating current, not a fuse rating. Motors and electronic power supplies may draw much higher starting or peak currents.
Cable length
Enter the one-way distance from supply point to load. The required return path is already represented by the selected formula.
Voltage
Enter the operating DC voltage of the complete PV string at its working point, not the voltage of one module. Check maximum open-circuit voltage separately.
Permitted voltage drop
This percentage limits the calculated voltage loss. It is a design assumption and must suit the circuit and applicable requirements.
Conductivity κ
κ is the calculation value for the conductor material. Common approximations are 58 for copper and 37 for aluminium; heating increases actual resistance.

Example: 12 A, 600 V and 25 m

At 12 A, 600 V, 25 m one-way copper and 1% voltage drop, 6 V is available.

A = (2 × 25 × 12) ÷ (58 × 6) ≈ 1.72 mm²

Voltage drop points to 2.5 mm². PV cable ampacity, DC rating, environment and connector system still need checking.

Treat PV DC voltage safely

String voltage varies with temperature. Maximum cold-weather open-circuit voltage is critical for insulation and equipment ratings.

Calculation limits

  • Maximum DC voltage, short-circuit current and safety factors are not checked.
  • UV exposure, routing, connectors and inverter requirements are excluded.