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Engineering Tool

Solar Cable Voltage Drop Calculator

Work out voltage drop on a DC string or single-phase AC run from the entered length, current, conductor size, voltage and material.

Sources listedReviewed July 2026Our methodology

Inputs

View result
Distance one way; the return conductor is included.
Use the conductor cross-section for the actual run.
Use the operating or design voltage for the circuit.

Live result

Edit inputs

Voltage drop

0.88V

Drop percentage

0.22%

Compare this result with the criteria applicable to the actual circuit and installation. Wattbench does not infer a permitted limit from these inputs.

Save or file this result
Key takeaways
  • Works out voltage drop on a DC string or single-phase AC run.
  • Uses run length, current, conductor size, voltage and material as inputs.
  • Returns the drop in volts and as a percentage without inferring the applicable design limit.

How it works

For a two-wire DC string or single-phase AC run, voltage drop is:

  • V drop = (2 × length × current × ρ) ÷ area, where the factor of 2 covers the active and return conductors, and ρ is conductor resistivity (~0.0175 Ω·mm²/m for copper, ~0.0282 for aluminium, near 20 °C).
  • Drop % = V drop ÷ system voltage × 100.

Real designs use the applicable temperature, installation method, conductor data and circuit criteria. Three-phase circuits also use a different factor. This tool reports the arithmetic result without inventing a pass limit; it is a first check, not a substitute for a licensed electrician's cable sizing.

Estimates only: for guidance, not a quote or a compliance certificate. Verify against the current AS/NZS standards and a licensed design. The maths runs in your browser. Nothing is sent to Wattbench unless you sign in and deliberately save the result.

Source ledger2 sources

Best next action

AS/NZS 3008.1Do this nextAS/NZS 5033Standard

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Frequently asked

Is this calculator free to use?
Yes. The voltage drop calculator is free and needs no sign-up. It runs entirely in your browser.
Is my data stored or sent anywhere?
The calculation runs in your browser. Nothing is sent to Wattbench unless you sign in and deliberately select Save result.
Does it support both DC and AC runs?
It works out two-wire DC or single-phase AC voltage drop from the values entered. It does not infer a permitted limit or replace a complete cable design.
Keep calculating

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