About the DC Cable Sizing
DC cable sizing selects the conductor cross-section for string and array cables so the current rating is safe and the voltage drop stays within limits — typically kept under 1–3% on the DC side to avoid energy loss.
Formula
A = (2 × ρ × L × I) ÷ V_drop
- A
- Conductor cross-section (mm²)
- ρ
- Resistivity of the conductor (copper/aluminium)
- L
- One-way cable length (m)
- I
- Cable current (A)
- V_drop
- Allowable voltage drop (V)
How to calculate it
- 1Take the string/array current and the one-way cable run length.
- 2Set the allowable DC voltage drop (typically 1–3% of the operating voltage).
- 3Solve for the conductor size, then round up to the next standard cross-section that also meets the current-carrying (ampacity) rating.
What you can calculate
- IEC 60364-7-712
- Temp derating
- Voltage drop
- Ampacity check
Standards & references
Frequently asked questions
What voltage drop is allowed for solar DC cables?
DC cable voltage drop is usually kept below 1–3% at operating conditions. Lower drop means less lost energy but larger, costlier cable — 1% is common for main array runs, up to 3% acceptable for short string cables.
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