Voltage Rise Calculator for the AC side of a solar inverter. It totals the rise in the inverter cable, submains and mains, then checks the 2% limit and the voltage at the inverter.
Enter the inverter's AC rating, not the panel kW. Lengths are one-way cable runs.
Mains and Submain
Other inverters add their current to these shared cables. Leave a length at 0 where a cable does not exist.
Limits and Grid Voltage
Output starts to drop at 253 V; enter 258 V to test the trip point. An export limit only applies to the consumer mains.
Voltage Rise by Cable Section
| Section | Cable | Current | Vc Used | Rise |
|---|---|---|---|---|
| Inverter Cable | 15 m of 6 mm² Cu | 21.7 A | 7.50 mV/A·m | 2.44 V (1.06 %) |
| Submain | Not used | None | None | 0 V |
| Consumer Mains | 12 m of 16 mm² Cu | 21.7 A | 2.81 mV/A·m | 0.73 V (0.32 %) |
Inverter Cable Size Chart
| Inverter Cable | Total Rise | Max Run | Result |
|---|---|---|---|
| 1 mm² | 7.64 % | 3.4 m | Over |
| 1.5 mm² | 5.00 % | 5.4 m | Over |
| 2.5 mm² | 2.87 % | 9.9 m | Over |
| 4 mm² | 1.91 % | 15.9 m | Pass |
| 6 mm² | 1.38 % | 23.7 m | Pass |
| 10 mm² | 0.95 % | 39.9 m | Pass |
| 16 mm² | 0.72 % | 63.4 m | Pass |
| 25 mm² | 0.57 % | 100.0 m | Pass |
| 35 mm² | 0.50 % | 138.8 m | Pass |
| 50 mm² | 0.45 % | 185.8 m | Pass |
| 70 mm² | 0.41 % | 264.2 m | Pass |
| 95 mm² | 0.39 % | 357.4 m | Pass |
| 120 mm² | 0.38 % | 438.9 m | Pass |
| 150 mm² | 0.37 % | 520.4 m | Pass |
| 185 mm² | 0.36 % | 613.7 m | Pass |
| 240 mm² | 0.35 % | 733.5 m | Pass |
| 300 mm² | 0.35 % | 828.2 m | Pass |
| 400 mm² | 0.35 % | 916.9 m | Pass |
| 500 mm² | 0.34 % | 987.5 m | Pass |
Voltage Rise Calculator for Solar Inverters
A solar inverter has to push its voltage above the grid to send power out, and every meter of AC cable adds to that push. The Voltage Rise Calculator totals the rise in each cable between the inverter and the supply point, then tests the result against the limit you set.
The default job is a 5 kW single-phase inverter on a 230 V supply. It feeds 15 m of 6 mm² copper to the switchboard, and 12 m of 16 mm² consumer mains run from there to the supply point. At 21.7 A the inverter cable adds 2.44 V and the mains add 0.73 V.
That totals 3.18 V, which is 1.38% of 230 V and inside the 2% limit of 4.60 V. With 245 V at the supply point the inverter terminals sit at 248.18 V. The same screen names 4 mm² as the smallest inverter cable that still passes and 23.7 m as the longest run on 6 mm².
What Is Voltage Rise and Drop?
Both are the same loss in the same cable, seen from opposite ends. When a load draws power, voltage falls along the cable toward the load, and that is voltage drop. When an inverter exports, current flows the other way, so the voltage is highest at the inverter and falls toward the grid.
The difference is in what gets checked. Drop is tested at the load with the building's maximum demand, and the Voltage Drop Calculator covers that case. Rise is tested at the inverter terminals with the inverter's rated output, against a much tighter limit.
Voltage Rise Formula
Australian cable tables give each size a voltage figure per amp per meter, written Vc and measured in millivolts. The voltage rise formula multiplies that figure by the cable length and the current.
L is the one-way length in meters, I is the inverter current in amps and Vc is in mV/A.m. Percent rise is the result divided by the nominal voltage, times 100. Inverter current comes from the AC rating, so 5 kW at 230 V is 21.7 A.
The Vc values in the Voltage Rise Calculator are the three-phase figures for multicore copper cable in AS/NZS 3008.1.1, the same numbers cable makers such as Nexans reprint in their handbooks. At 75 °C, 6 mm² lists 6.49 and 16 mm² lists 2.43. The standard's note says to multiply by 1.155 for single phase, which gives the 7.50 and 2.81 shown in the section table.
Three-phase inverters use the table value directly, and the current is the rating divided by 1.732 times the line voltage. The 2025 edition of AS/NZS 3008.1.1 added its own clause on voltage rise with two worked examples, so the method now sits in the cable standard as well as the solar one.
The 2% Limit in AS/NZS 4777.1
In Australia the number to beat is 2%. AS/NZS 4777.1 requires that the overall rise from the point of supply to the inverter AC terminals stays within 2% of nominal voltage, which is 4.6 V on a 230 V supply and 8 V on 400 V. Used as an AS4777 voltage rise calculator, the tool defaults to that figure.
The check covers the whole path. NT WorkSafe spells it out in a technical update, listing the full length of the consumer mains, any submains and the cable to the inverter. It also warns that a system outside the limit can shut down again and again.
Training body GSES notes that Appendix C of the standard works examples for single-phase, three-phase and multiple-inverter systems. Some network rules go further. The NSW Service and Installation Rules aim for 1% on the consumer mains and 1% from the main switchboard to the inverter, and Allowed Voltage Rise accepts any target from 0.1% to 10%.
Each Circuit Section Adds Its Share
The Mains and Submain panel holds the cables upstream of the inverter circuit. Enter a length and size for each one that exists and leave the others at 0. The section table in the Voltage Rise Calculator then lists the current, the Vc used and the volts added by each part, with the largest contributor highlighted.
On the default job the inverter cable is responsible for 2.44 V of the 3.18 V. That tells you where money is best spent, because upsizing the mains from 16 mm² would recover only a fraction of the 0.73 V they add.
An export limit changes one section only. With a 3 kW limit on the 5 kW inverter, the consumer mains carry 13.0 A and their share falls to 0.44 V. The inverter cable still carries the full 21.7 A, since loads in the building can use the rest, and the total comes to 2.88 V or 1.25%.
Two more fields deal with shared cables. Other Inverters on This Board adds a second unit's current to the mains and submain, so a second 5 kW inverter doubles the mains share to 1.46 V and lifts the total to 1.70%. Consumer Mains in Parallel splits the current across up to six cables, and two cables cut that share in half.
Grid Voltage and the Inverter Limit
A cable result inside 2% does not guarantee the inverter stays at full output. What the inverter sees is the grid voltage at the supply point plus the rise, and the first card of the Voltage Rise Calculator adds the two.
The upper limit defaults to 253 V, which is 230 V plus 10%. Network operators such as Jemena publish the Australia A settings from AS/NZS 4777.2. Volt-watt response begins cutting output at 253 V and reaches 20% at 260 V, and the inverter disconnects when the 10 minute average passes 258 V.
The row named Supply Voltage at Limit turns this into one number, which is the part most voltage rise calculator results leave out. On the default job it reads 249.82 V, so a grid above that pushes the inverter past 253 V. Raise the grid voltage to 250 V and the result changes to Cables Pass, Grid Voltage Is High. Bigger cable gains little at that point, and the network operator is the one to call.
Fixing a Result Over the Limit
Stretch the default inverter cable from 15 m to 30 m and the total climbs to 5.62 V, or 2.44%. The Voltage Rise Calculator answers with the fix, 10 mm² on the inverter cable, which brings the total back to 1.58%. Its size chart shows every listed cable at once with its total rise and longest run.
Phase choice matters more than cable on larger systems. A 10 kW single-phase inverter on the default cables draws 43.5 A and reaches 2.76%. The same 10 kW on a 400 V three-phase supply draws 14.4 A per phase and comes in at 0.46% on identical cable.
Conductor temperature moves the answer slightly. Selecting 90 °C for XLPE cable raises the default result from 1.38% to 1.45%, because resistance climbs as the conductor heats. Cable current ratings are a separate check, and the Wire Ampacity Calculator and Wire Size Calculator cover it.
US Solar Circuits in AWG and Feet
Switching Wiring Standard to NEC Table 8 turns this into a voltage rise calculator for solar work in the US. Sizes change to AWG and kcmil, lengths to feet, and the upstream cables are renamed Feeder and Service. Resistance comes from NEC Chapter 9 Table 8 at 75 °C, doubled for the out and back path on single phase.
The NEC sets no voltage rise limit, so the 2% target here follows inverter makers. Enphase tells installers in its voltage rise technical brief to calculate each section and keep the total under 2%.
The US default in the Voltage Rise Calculator is a 5 kW inverter at 240 V, which is 20.8 A. Sixty feet of 10 AWG copper adds 3.10 V and a 40 ft feeder in 6 AWG adds 0.82 V, for 3.92 V or 1.63%. A 7.6 kW inverter on the same wire reaches 2.48%, and 8 AWG on the inverter run brings it to 1.75%.
The upper limit in this mode defaults to 264 V, 110% of 240 V, against a 246 V grid. Metric and AWG sizes do not line up one for one, so the AWG to mm² Calculator helps when a plan uses one system and the cable on the truck uses the other.