Inverter AC cable voltage drop calculator

Use this page when an inverter AC cable run needs a traceable voltage-rise or voltage-drop record before the result is carried into a cable schedule, quote review, commissioning pack or DNSP discussion. The calculation is only as strong as the inverter current basis, route length and cable data entered by the user.

The common solar question is not simply "what is the voltage drop?". For an exporting inverter, the practical issue is often voltage rise at the inverter end of the AC cable. The same cable formula gives the magnitude, but the record must say whether that magnitude is being added for export-rise review or subtracted for load-drop review.

Field use cases

A useful inverter AC cable record is specific. "Voltage rise looks fine" is weak. "INV-AC-1, 5 kVA single phase, 20 m one-way route, 2.8 mV/A/m project cable data, 1.22 V rise, 0.53% against entered 1.0% target" can be reviewed and repeated when the route, inverter or cable data changes.

Inverter AC data checklist

Do not mix cable data from one conductor arrangement with a different route or installation assumption. If the source value is mV/A/m, it should already match the circuit context used by the project source. If the source gives resistance and reactance, enter both values and keep the source visible in the record.

Voltage rise and voltage drop interpretation

For an exporting inverter, the calculated cable voltage change is normally read as voltage rise toward the inverter terminals. The calculator adds the cable change to the entered nominal voltage and reports an estimated endpoint voltage. That value is a worksheet estimate, not a measurement of actual network voltage.

For load direction, the same cable magnitude is read as voltage drop. The calculator subtracts the cable change from nominal voltage. This is useful for a hybrid or backup context where the AC run is being reviewed in a load direction, but it should not be confused with the usual grid-export voltage-rise discussion.

The percentage result is often the most useful comparison value because it lets the same run be checked against the project target entered by the user. A negative target margin means the calculated percentage is above that target. That is not an automatic compliance outcome, but it is a practical stop point for route length, cable data, inverter current and project requirements.

Cable data source matrix

The calculator deliberately does not embed a cable table. Cable data stays user-entered because Australian inverter AC cable checks depend on the selected cable source, conductor, insulation, installation method, grouping, ambient conditions, protection and project documentation.

Target review matrix

This matrix is not a compliance table. It is a review aid that helps identify which input is driving the result. Actual inverter operation can also be affected by network voltage, inverter settings, export limits, site loading, phase balance and DNSP requirements.

Review workflow

1. Identify the inverter AC run reference from the cable schedule, switchboard schedule or drawing.
2. Select export voltage rise unless the project is specifically reviewing load-direction voltage drop.
3. Enter the phase arrangement and nominal voltage used in the project basis.
4. Enter inverter current directly where available; otherwise enter kVA or kW with the power factor basis visible.
5. Enter the one-way route length between the inverter and the connection point being checked.
6. Enter cable data from the project source as mV/A/m or as resistance and reactance.
7. Enter the project voltage-rise/drop target being used for comparison.
8. Read the voltage-change percent, target margin and endpoint voltage together.
9. If the margin is negative or narrow, review route length, cable data and current basis before changing documentation.
10. Keep DNSP conditions, current standards, inverter manufacturer requirements and final cable selection as separate checks.

This workflow keeps the calculator as an arithmetic worksheet. It does not decide cable size, approve the connection point, set inverter controls or replace commissioning checks.

Worked records

The examples show why route length and current basis matter. The calculation is not a generic solar answer; it is a record for one inverter AC cable run with a named source of cable data.

Boundary with neighbouring calculations

Keeping this boundary clear prevents the inverter AC cable worksheet from becoming a connection approval tool. The result shows whether the cable-run arithmetic is tidy enough to carry forward without pretending to close the project.

Australian context

Grid-connected inverter work in Australia sits inside current Australian standards, local authority requirements, DNSP conditions, network voltage conditions, equipment documentation and manufacturer instructions. AS/NZS 4777.1:2024 and AS/NZS 4777.2:2020 are relevant context for inverter energy systems, while AS/NZS 3008.1.1:2025 is relevant context for cable data and cable selection. DNSP service rules and connection processes can still govern the project outcome.

This page keeps the public calculation transparent. It does not reproduce controlled standards content, does not encode network-specific voltage-rise limits and does not state that an inverter run is acceptable. It records the arithmetic from the values entered by the user so the result can be reviewed with the proper project documents.

In practice, this record usually sits beside the inverter datasheet, cable schedule, switchboard schedule, site route measurement and connection-point documentation. The worksheet helps identify whether the cable-run arithmetic is worth carrying forward; it does not replace network voltage evidence, inverter settings review, current-carrying-capacity checks or manufacturer instructions.

Stop points

• The inverter AC current or rating basis is unknown.
• The one-way route length is estimated loosely and the result is close to the entered target.
• Cable data is copied from a different conductor, arrangement or installation assumption.
• The calculated percentage is above the entered project target.
• Endpoint voltage is being treated as a measured network voltage.
• DNSP connection requirements, export limits or inverter settings are being treated as optional.
• The result is being used as final cable selection without checking current-carrying capacity, protection, installation conditions and manufacturer instructions.