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DC Cable Size & Voltage Drop Calculator

Recommended cable size

6 mm² (≈10 AWG)

Your recommended cable size comes out to about 6 mm² (≈10 AWG).

Min 4.4 mm² for 3% · 10 AWG

Voltage drop %

2.19%

1.05 V drop · 47 V at load

Power loss (watts)

12.6W

I²R · 12 A · 15 m one-way

Within your 3% DC drop target—good for MPPT and charge controllers.

Why voltage drop matters

On DC solar homeruns, every volt lost in the cable is a volt your MPPT or charge controller never sees. Beyond the usual 3% planning limit, undersized copper runs hot (I²R loss), which raises insulation temperature and fire risk on roof trenches and long array feeds.

We size for your amp load, one-way length in meters, and max drop target, then snap to the next standard mm² / AWG with enough ampacity for continuous DC.

  • Round-trip resistance: panel → controller and return conductor
  • Power loss (W) is wasted heat in the cable—size up to stay cool
Solar Panel Size — match array to daily energy

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How this calculator works

How to use the DC Cable Size & Voltage Drop Calculator

The Formula

Voltage drop on the PV homerun reduces power available to the controller. This tool computes minimum copper cross-section for your max drop %, then reports actual drop and I²R watts on the recommended standard cable.

Practical Example

Copper at ~20 °C, round-trip path (out and return). Ampacity limits are conservative planning values—follow local code and manufacturer tables for final installs.

About DC Cable Size & Voltage Drop Calculator

DC drop and solar yield

Voltage drop on the PV homerun reduces power available to the controller. This tool computes minimum copper cross-section for your max drop %, then reports actual drop and I²R watts on the recommended standard cable.

Sizing assumptions

Copper at ~20 °C, round-trip path (out and return). Ampacity limits are conservative planning values—follow local code and manufacturer tables for final installs.

Frequently asked questions

Q: One-way or round-trip length? A: Enter one-way meters; resistance uses both conductors. Q: mm² or AWG? A: We show both on standard sizes. Q: Full system design? A: Pair with Solar Panel Size for array wattage.

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