24V Wire Size Calculator

Doubling the voltage halves the current for the same power and doubles the voltage-drop budget, so a 24 V run can be a quarter of the cross-section of the 12 V one, or four times as long on the same cable. That is the whole case for 24 V over 12 V, and it is why boats and cabins with a real inverter tend to end up here.

This is the solar cable size calculator set up for 24 V: the tool opens on the 24 V boat or cabin preset: 60 A over 20 ft at a 2% limit. Change anything you like; the tables below are fixed at 24 V.

Free download

Get the printable solar cable and fuse charts

DC cable ampacity with the ambient and bundling corrections, how far each size runs at 12, 24 and 48 V, PV string fuse sizes from Isc, and battery-to-inverter current by inverter size. Three pages, made to pin by the battery bank.

We store your email with EmailOctopus to send the charts and occasional solar sizing tips, nothing else. Unsubscribe any time. Privacy policy.

The three runs at 24 V

Every solar build has the same three DC legs. These are sized at the currents and lengths the calculator's own presets use, copper, 75°C conductor, 30°C ambient, three conductors, terminal rating per NEC 110.14(C). Change the current or the length and the answer moves; that is what the tool above is for.

Run Current One-way length Drop limit Copper size at 24 V Set by
Array to charge controller 30 A 40 ft 3% 3 AWG voltage drop (48 ft max)
Controller to battery 60 A 10 ft 2% 4 AWG both (12 ft max)
Battery to inverter 125 A 6 ft 2% 1 AWG ampacity (130 A at 75°C)

At 24 V the two limits trade places more often than at either 12 V or 48 V: short, high-current battery runs are set by ampacity and anything over about 20 ft is set by drop. Check which one the calculator reports as binding, because the fix is different: a shorter run for drop, a bigger cable or a cooler route for ampacity.

Worked example

The inverter sizing calculator's worked example is a 2,500 W inverter on a 24 V bank at 90% efficiency: 116 A at the inverter's rating and 208 A during a motor-start surge. Sized as a continuous load at the rating over a 6 ft run at 2%, that is 1 AWG copper, set by ampacity rather than by drop. The same inverter on 12 V would draw 231 A continuous and need parallel 4/0 runs.

What each inverter size draws from a 24 V bank

The battery-to-inverter leg carries the highest current in the system, and it is sized on the current at the inverter's rated output and at the bank's lowest voltage, because that is the worst case the cable and the fuse have to survive. At 24 V nominal the low-voltage cutoff defaults to 21.0 V, which is 87.5% of nominal, and the inverter sizing calculator's own default efficiency is 92%.

DC input current, cable size and overcurrent device for each inverter rating on a 24 volt bank
Inverter DC amps at 24 V DC amps at 21.0 V cutoff Copper, 6 ft at 2% Device at 125%
1,000 W 45 A 52 A 6 AWG 70 A
1,500 W 68 A 78 A 3 AWG 100 A
2,000 W 91 A 104 A 2 AWG 150 A
3,000 W 136 A 155 A 2/0 AWG 200 A
4,000 W 181 A 207 A 4/0 AWG 300 A

Every row here is half the current of the same inverter at 12 V, which is what buys 24 V its extra headroom: a 3,000 W inverter is a manageable cable and fuse at 24 V and a parallel-conductor problem at 12 V. Past about 4,000 W the currents start looking like the 12 V table did at 2,000 W, and that is the point at which 48 V is the cheaper answer.

How far each cable runs at 24 V

Maximum one-way run in feet before voltage drop reaches 3% (0.72 V) on a 24 V DC circuit, copper. Greyed cells are currents the cable cannot carry at a 75°C termination, so length is moot. Design the battery-to-inverter leg to 2%, which is two thirds of these figures.

Maximum one-way run length in feet at 3 percent voltage drop on a 24 volt DC circuit, copper conductors, by current
Copper size 75°C ampacity 10 A 20 A 30 A 60 A 100 A 150 A
10 AWG 35 A 30 ft 15 ft 10 ft — — —
8 AWG 50 A 46 ft 23 ft 15 ft — — —
6 AWG 65 A 73 ft 36 ft 24 ft 12 ft — —
4 AWG 85 A 115 ft 57 ft 38 ft 19 ft — —
2 AWG 115 A 190 ft 95 ft 63 ft 31 ft 19 ft —
1/0 AWG 150 A 302 ft 151 ft 100 ft 50 ft 30 ft 20 ft
2/0 AWG 175 A 357 ft 178 ft 119 ft 59 ft 35 ft 23 ft
4/0 AWG 230 A 581 ft 290 ft 193 ft 96 ft 58 ft 38 ft

Resistances are NEC Chapter 9 Table 9 values; DC resistance is marginally lower, so these lengths are slightly conservative. Ampacities are NEC 310.16 for not more than three current-carrying conductors at 30°C, before the ambient and bundling corrections the calculator applies when you change those fields. For the drop on a run you already have, use the DC voltage drop calculator; to protect the run, the PV fuse and breaker calculator.

Frequently Asked Questions

What size wire do I need for a 24 V solar system?

It depends on the run, not the system. At 24 V the array-to-controller leg at 30 A over 40 ft needs 3 AWG copper, and the battery-to-inverter leg at 125 A over 6 ft needs 1 AWG. A 3% budget at 24 V is only 0.72 V, so the run length decides the array cable and the current decides the battery cable. Enter your own current and length in the calculator above.

How far can I run 10 AWG at 30 A on 24 V?

About 10 ft one-way before the drop reaches 3%, and about 6 ft at a 2% limit. Beyond that, step up one size per further increment of length; the run-length table above shows where each size gives out at 24 V.

Where is 24 V the right system voltage?

Boats, larger vans, cabins with a 1 to 3 kW inverter, and off-grid systems that have outgrown 12 V but do not need 48 V hardware. Higher voltage means lower current for the same power, so the practical question is how much inverter you run: the DC current at the inverter's rating and at its low-voltage cutoff sets the battery cable and the fuse, and that number is what pushes bigger systems up to 24 V and 48 V.

Does this include ambient temperature and bundling derating?

The tables on this page do not; they are the NEC 310.16 base values at 30 C with three conductors. The calculator above does: change the ambient temperature and the conductor count and it applies the NEC 310.15(B)(1)(1) and 310.15(C)(1) factors, which matter on a hot roof or in an engine bay, and it caps the answer at the terminal rating per NEC 110.14(C).

Is 24 V worth it over 12 V for a boat or a cabin?

Once the inverter passes about 1,500 W, usually yes. At 24 V the battery-to-inverter cable, the fuse and the busbars are all half the current of the 12 V equivalent, a 60 A charge controller handles 1,440 W of array instead of 720 W, and every run can go twice as far on the same cable. The costs are 24 V appliances being rarer than 12 V ones and needing a DC-DC converter for the 12 V loads you keep.

Can I keep my 12 V fridge and lights on a 24 V system?

Yes, through a DC-DC converter, and that is the usual arrangement on a boat: a 24 V bank for the inverter, the windlass and the charging, with a converter feeding a 12 V distribution panel for the electronics and lighting. Size the cable on each side at its own voltage, because the 12 V side of the converter carries twice the current of the 24 V side for the same load and is the leg that needs the bigger conductor.

Cable size at other system voltages

12 V wire size 48 V wire size Any voltage

Related Calculators

Continue with these related solar tools

Solar Cable Size Calculator

Smallest DC cable that carries the current and stays inside your voltage-drop limit (AWG/mm2)

DC Voltage Drop Calculator

Voltage drop on 12V, 24V and 48V DC runs by cable length, current and conductor size

Inverter Sizing Calculator

Continuous and surge inverter rating from your load, plus the DC input current the battery cable has to carry

PV Fuse and Breaker Sizing Calculator

Next standard fuse or breaker size for a PV string, controller or inverter circuit

Solar Sizing Calculator

Free solar and off-grid sizing calculators

More Calculators

© 2026 Solar Sizing Calculator. All rights reserved. A Nomogram Works site.

Privacy Policy Terms of Service Cookie Policy