DC Cable Sizer
Copper cross-section for <2% voltage drop
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Circuit Parameters
Size the DC run from array junction to inverter. Distance is one-way cable route length — the return path is accounted for automatically.
Formula: A = (2 × L × I × ρ) ÷ (V × 2%), copper ρ = 0.0186 Ω·mm²/m at operating temperature, rounded up to the next standard size. Verify ampacity and derating per IS 694 / cable manufacturer tables for the final BOM.
Required copper cross-section
2.5mm²
Calculated minimum 1.61 mm² → rounded up to the standard 2.5 mm² size
Actual voltage drop
1.29%
7.7 V lost end-to-end
Conductor length
80 m
out + return path
Resistive loss
101 W
dissipated in the cable
Standard size ladder
About This Calculator
Every metre of undersized cable is a permanent, invisible tax on generation. This calculator applies the standard voltage-drop formula — A = (2 × L × I × ρ) ÷ (V × 2%) — to return the minimum copper cross-section for a DC run, rounded up to the next standard size (4 mm², 6 mm², 10 mm²…), along with the actual voltage drop and watts dissipated in the cable.
The 2% DC voltage-drop ceiling is the design norm for quality Indian installations. The tool accounts for the out-and-return conductor path automatically — you enter the one-way route length. Always cross-check the chosen size against ampacity and derating tables (IS 694 / manufacturer data) for the final bill of materials.
Frequently Asked Questions
- Why 2% and Not More?
- Voltage drop is energy converted to heat in the cable — every day, for 25 years. The industry norm caps DC drop at 2% (and total system drop at ~3%) because beyond that, the lifetime energy loss outweighs the cost of thicker copper.
- Copper or Aluminium for Solar DC Cables?
- Copper for rooftop DC runs — better conductivity, smaller cross-sections, and compatible with standard MC4 ecosystems. Aluminium appears mainly in large ground-mount AC transmission where its cost advantage justifies the larger sizes.