PV DC voltage drop distance calculator

Preliminary estimate

Inputs

Calculation note

This is a distance screen for PV DC voltage drop. PV wire, protection, temperature, and installation requirements still need separate review.

Method

Allowed Vdrop = array voltage x allowed percent / 100

One-way metres = allowed Vdrop x A / (2 x K x I)

Round-trip metres = one-way metres x 2

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Formula variables

  • A is conductor area in mm2.
  • K is material resistivity in ohm mm2/m.
  • I is PV DC current in amperes.
  • Allowed percent is the voltage-drop target used for the distance screen.

Assumptions

  • The calculator rearranges the DC voltage-drop formula to solve one-way run length.
  • Allowed voltage drop is entered as a percent of nominal array voltage.
  • The result is a voltage-drop distance screen before product, temperature, installation, and protection checks.
  • This calculator does not choose PV wire, protection, disconnects, temperature treatment, wiring method, or installation approval.

Examples

600 V PV DC run. At 600 V, 20 A, copper 6 AWG, and a 3 percent drop target, the maximum one-way distance estimates about 347.1 m.

Tighter drop target. A 1 percent target shortens the allowable run and may require a larger conductor or different array/inverter layout.