# What is the Maximum Cable Length to Use with your Solar Panels?

If you’re installing your own off-grid solar system, you may need to use longer cables from the solar panels to the charge controller should you, for instance, need to mount the solar panels away from trees or other obstacles casting shade on them to get maximum power

What is the maximum cable length you can use? Are there any rules of thumb you can use in working out the size of the cable?

This post provides some tips and a calculator to use to select the optimum length of cable to use to minimize power losses from solar panels.

## How Long Should the Solar Panel Cables Be?

There’s no one answer to the maximum cable length of solar panels to charge controller as the cable length depends on:

• the current that’ll flow through from the solar panels. The more amps, the shorter the cables should be for a given wire size (AWG). You could also reduce the current flow from the solar panels by connecting them in parallel instead of series and therefore able to run longer cables.
• The wire size (AWG). You can run longer solar panel cables by using thicker wire sizes.

This depends on the current (amps) from the array and the size of the wire you plan to use (AWG).

You can use the calculator below to work out for a given voltage drop (3% or 10%) what wire size you should use depending on the wire length.

Worked Example

Suppose you have 400 watts of solar panels from 4 pieces of 100-watt solar panels connected in parallel each with an optimum operating current of 4.91A (check the panel specifications).

The combined current flow from the four solar panels is 19.64 amps (4.91A x 4).

For a return length of solar panel cables to the charge controller of 45 ft (one cable length is 22.5 ft), then using the calculator above, for a 3% voltage drop, the cable length is 6AWG.

Should you opt to work with a 10% voltage drop, then use a 12AWG cable.

## Why You Shouldn’t Exceed the Recommended Cable Length

1. The Charge controller or appliance may not work properly

If you use a longer cable run for a given current flow and wire size (AWG), expect a larger voltage drop. The implication is that the voltage reaching the appliance will be lower and the appliance may not work properly.

Use the wire size calculator above. Keep the acceptable voltage drop and current flow fixed and change the cable length (always combine the cable length of wire from the positive terminal and the negative terminal) to view what wire size you should use to maintain the voltage drop.

2. Longer cable runs are more expensive

You’ll need thicker and more expensive cables to maintain a voltage drop which requires a larger investment in cables.

Thicker cables are often difficult to bend and in general to work with too and may not easily connect to the charge controller or inverter terminals!

Related Questions

## The Maximum Solar Panel Cable Length to Use with 10 AWG

No one straight answer as it depends on the:

• output current from the solar panel array i.e. how many watts of solar and whether it is connected in a 12V, 24, or other voltage configuration,
• wire size (AWG)
• and the length of the cable.

Using the calculator, for a return length of 50ft and limiting the voltage drop to 3%, you should limit the current drop to 5 amps when using 10 AWG wire.

What if you already have the cables and have a voltage drop problem, how do you fix it?

Increase the voltage drop at the solar panels (make sure the charge controller can handle the higher voltage though!)

For example, to limit the voltage drop to 3% for the case of 4 pcs of 100-watt solar panels connected in parallel (Output voltage 20.4V and combined current of 19.64A), one-way cable length of 22.5 ft, you need a 6AWG cable.

Should you connect them in series for a combined output voltage of 81.6V (limit the current to 4.91A) then you can use a 10AWG cable while limiting the voltage drop to 3%.

*Note Check the solar panel specifications for their combined current flow.

## Closing Thoughts

There is no hard and fast number for the maximum length of cable you should use to connect the solar panel to the charge controller as this depends on the amps that the cables are handling, the wire gauge used, and acceptable voltage drop.

To increase the distance of the wires from the solar panels to charge controllers, use thicker cables or increase the system voltage. Make sure the charge controller can handle the higher voltage.

Note too that thicker cables increase the investment cost in cabling.

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