What Size Cable For 12V Solar Panel?

What Size Cable For 12V Solar Panel?

One of the most critical parts of getting solar power is wiring. A lot can go wrong if you do not select the correct wire size, let alone install the wires incorrectly. Hence, choosing the correct wire gauge is crucial for the safety and functionality of your solar PV panels.

If you have a 12 V system, you might be confused about what cable to hook it up to. This article will teach about choosing the correct wires for solar power and more.

Let’s get started.

dc solar cables

About Solar Wires

Before we jump into what size wire you should get for your solar system, let’s talk about solar wires in general. Solar wire sizes are standardized using the American Wire Gauge and are constructed from copper wire.

Generally speaking, wires with higher numbers have more resistance. At the same time, high gauge numbers can securely deal with lower currents only.

As a result, different solar systems need different wire sizes. Additionally, different parts of the solar system may require different wire sizes, such as a regular panel versus a battery bank. This applies to both diameter and length.

Solar power typically needs a 12 gauge AWG wire, though the cable size may differ based on specific factors, like resistance and flow.

solar cabling

What You Need To Understand To Estimate What Wire Gauge You Need

To know what wire size you need to get your solar power, there are three main terms you need to know first. Take a look at each of these terms that will all be important for picking out the suitable solar wire:

System Voltage

System voltage is the electric potential difference. In more simple terms, it is the difference between the electrical charge’s two circuit ends.

Voltage Drop Index

The voltage drop index tells you how much an undersized wire will reduce the voltage. A reduction in the voltage causes the wire’s voltage to drop and the power to be lost.

Maximum current

Much like the ocean current, an electrical current flows between the electrical circuit. Whenever you look at the formula used to determine wire size, maximum current is often represented with “I.” Likewise, a current tells you the flow rate expressed in amps.

The Formula

The formula that I will use in this article is as follows: Amps = Watt / Volt.

We will use this formula to find the amperage, wattage, or voltage, according to which variables are missing or unknown. For example, you can find the wattage if you know the voltage and amp or the amp if you know the watts and voltage.

This formula is essential because you must know the amp to determine the wire size for your solar panel. Therefore, throughout the rest of the examples, we will refer back to this formula to determine the exact power output and wire size of a 12 V panel.

solar cabling 2

What Cable Should I Use For 12V?

Unfortunately, knowing what cable you should get for your solar power requires more knowledge than just the voltage. Generally speaking, most residential solar systems are good with wires between 8 and 14 gauges, depending on the exact wattage and amperage.

You need to look at the amp to know which cable to get. The amp tells you the minimum AWG you should get based on a 2% voltage drop.

How Many Amps Does A 12V Solar Panel Put Out?

So, you must figure out how many amps the 12 V panel puts out before learning about the wire the panel requires. You will need to do some basic math to find out the amp.

Using the formula above, divide the wattage by the voltage. In this scenario, the solar power system has 12 volts and a Vmp of 18. We still do not know the watts required to know the amp. The wattage will be determined by your specific needs and uses.


Let’s say that you have a 100 Watt 12 V panel. The Vmp is 18V. So, divide 100W by 18V, and you get about 5.5 amps. Assuming you only need 100 watts of power, you could use a 14 AWG solar wire.

We concluded this because a 14 AWG wire with a 2% voltage drop capacity is 15 amps. Given the math we did above, the amp in the scenario is far below the capacity of a 14 AWG wire.

You Do The Math

Now, you will need to do the math for yourself. First, replace the 100W with however many watts your solar panel needs. Then, calculate your amp. Most likely, you will need a cable between 10 and 14.

cable installation for solar rooftop system

What Size Wire Do I Need For a 200 Watt Solar Panel?

Above, we learned how to calculate the amp and wiring for a solar system with 12 V. Now, let’s apply that same formula and math to a solar power panel of 200W.

In most scenarios, solar PV panels are 12 V. Now, we know the watts, allowing us to understand better the amp and wire size needed for the system.

Like before, divide 200W by 18Vmp. When you do this, you will learn that the amperage is around 11. Like before, you can use a 14 AWG cable according to the 2% voltage drop chart.

You may need to use a 24-volt panel instead. Adjust our math above and calculate if that applies to you;

Can I Use 14 Gauge Wire For Solar Panels?

Technically, you can use a 14 gauge solar wire for panels, but it can only handle 15 amps. Many solar panels need a higher amp. So, using a 10 or 12 AWG wire may be better for the best results on standard solar panels.

As we saw in the two examples above, there are plenty of times when a 14-gauge cable works perfectly fine for solar panels. So long as the expected maximum amp is below 15 amps, a 14 gauge wire should work perfectly fine for solar PV panels.

You can jump up to a 12 gauge wire if you aren’t sure you will exceed 15 amps. 12 AWG wires have an amp capacity of 20 with a 2% voltage drop.

When 14 Gauge Wires Are Not Acceptable

That said, a battery bank will be unsuitable with a 14 AWG wire. Instead, a solar battery bank will likely need a 3/0 AWG cable. Like the battery bank, the charge controller needs between 3 and 8 AWG wires.

The charge controller is what allows solar battery storage to work. If you do not have a charge controller or solar battery system, then you don’t have to worry about this step, though you don’t have to worry about power loss due to loss of sunlight with a solar battery system.

Still, all solar system users have to think about the cable size based on the part of the system, such as the battery bank and charge controller.

What About Wire Length?

There’s still one missing piece to our puzzle: wire length. PV array amps tell you how long the cable can be. But, as we learned above, the length of the cable is just as important as the diameter.

You will need to look at a voltage drop chart to see a table about cable length based on the PV array amp. The length of your wire can not be ignored. The amp may be suitable for a 14 gauge cable does not mean a 14 gauge wire will work for the whole system.


Let’s say that your solar panel is expected to use ten amps. If so, your cable length can only be 4.5 feet with a 14 gauge cable. Unfortunately, 4.5 feet is not enough room for most solar panel cables. So, you will likely need to select the 10 or 12-gauge wire instead.

In comparison, the 12 gauge wire can be 7 feet long if the panel has an amperage of 10. Similarly, the 10 gauge wire has an impressive 9.5-foot maximum length with the same amp.

What Does This Mean?

So, how does this affect choosing the suitable cable for your solar panel? Well, it tells you that you must consider the cord’s diameter and length when selecting the correct wire for your solar panel.

Once you know the amp, determine which cable size is best for your unique solar panel system.

Is There An Easier Way? Yes – Calculator

You can always use a gauge calculator online if you do not trust yourself to calculate the cables. First, you will need to type in the inputs in the calculator. Then, the calculator will compute the results for you, making it a bit easier and relieving the need to look at a voltage drop chart.

Final Thoughts

Picking out a suitable cable for your solar panel is difficult. It requires math and a bit of knowledge about your energy expenses. However, once you can fill out the information needed to locate your maximum amperage, you can easily find the right cables based on diameter and cable length.

Use a calculator if you are worried!

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