When you are creating your 200 W monocrystalline solar panel array, you might be thinking about things like how much does a 200-watt solar panel cost, and how many you will need. The size of the wire you will need may be the last thing that is on your mind.

But, wire size actually plays a very important role in the functioning and safety of your 200-watt solar panel system, and can even be more important than figuring out “How many batteries do I need for a 200-watt solar panel?”

The wire size you need is unique to your solar panel system, and the wire size will be different for a 100 vs 200-watt solar panel, it is not a “one size fits all”.

To help make sure that you select the correct wire and that your solar panel functions at its optimal capacity, we will be explaining the best method to figure out what wire size is right for your 200-watt solar panel, as well as why it is so important to correctly size your wires. 

What Does “Wire Size” Refer to?

When we say “wire size” we are largely referring to the diameter of the wire, but are also referring to the length of the wire.

This diameter size is also referred to as “gauge wire”. Gauge wire is sized according to a gauge scale that is called the American Wire Gauge, often shortened to AWG.

The gauge of your wire will determine what amount of electrical current is safe to be conducted through the wire. 

If there is too much electrical current that is transported through the wire, it can lead to the wire being damaged, or can even be the cause for the start of an electrical fire. 

Another element that the size of the wire determines is the wire’s resistance and its weight per unit of length. 

The AWG scale rates wire gauge in whole numbers. The size of the number is inversely proportional to the diameter of the wire.

This means that the higher the gauge wire number, the smaller the diameter of the wire will be. 

A smaller diameter will also lead to more resistance to the flow of current, as the two are also inversely proportional. So, as the diameter of your wire decreases, the resistance will increase, and vice versa for when the diameter increases.

In general, a larger wire diameter is usually the safer route to go. This is because it has less resistance and is less likely to be a safety hazard or cause a fire. 

The only problem is that larger diameter wires are also more expensive because they obviously require more materials to make. 

So it will be important for you to find a midpoint of what wire size is large enough to know it will be safe but also won’t cost you an arm and a leg. 

Lastly, it is also important that you note that the AWG number only accounts for the diameter of the copper wire, not the insulating material that will be used to cover the wire. 

How to Calculate Wire Size for a 200-Watt Solar Panel

The first thing to note is that the wire size won’t be the same for every piece of wire in your solar array. 

The wire size will differ at different sections of your setup, and it is important that you size each section correctly.

Important Elements to Look at Before Calculating Wire Size

When calculating wire size, the aspects of your solar system that you need to know is what your 200-watt solar panel’s output voltage is (this is usually 12, 24, or 48 volts), the total amps that your solar panel will produce, as well as how long this specific piece of wire will need to be. 

Different gauge wires can only withstand a certain level of voltage and amperage, which is why it is crucial to look at your solar panel’s specifications before calculating wire size.

For example, if you take the 200 Watt Eclipse Solar Panel Suitcase, which is available from Shop Solar Kits, the maximum voltage is 17.7 volts, and the maximum amperage is 10.35 amps. 

This means that the gauge wire has to be able to withstand both of these measurements in a safe, yet efficient, manner.

Different Ways You Can Calculate Wire Size

Wire size can be calculated manually, or it can be calculated through an online wire size calculator. 

The latter is the more popular option in almost all cases. 

Manually calculating wire size can be done if you so wish, but it is a very long, drawn-out way of doing so, and it makes room for a lot of errors along the way, as it is quite complex.

We will, however, be providing you with an example of how to manually calculate wire gauge if you so wish to do so.

Regardless of the method you choose, you will still need to know the elements we spoke about earlier, which are the voltage, amperage, and length of the wire, before you do any calculations.

How to Manually Calculate the Wire Size for a 200-Watt Solar Panel

For this example, we will be using Shop Solar Kit’s 200 Watt Eclipse Solar Panel Suitcase that we spoke of earlier.

This 200-watt solar panel has a maximum voltage of 17.7 volts and a maximum amperage of 10.35 amps.

Also for the sake of this example, we will assume that a 12 V battery is being used, and we are calculating the wire gauge for a wire that runs between the battery and the solar panel, and needs to be 60 meters long.

First off, we will have to work out the target resistance. This is done by using ohm’s law, which has a formula of V = I x R. in our case, the equation will be 17.7/10.35 = 1.71 ohms.

This gives us an idea of how much resistance will be given off by this solar panel.

The most common material used for solar panel wiring is copper, so we will assume that this is the material that we will be using too.

The resistivity of copper is 1.724 x 10^-8 ohm meters at room temperature, and you will have to multiply this by the meters that the wire needs to be. As we mentioned, in this case, we will say that the wire needs to be 60 meters long. 

60 x 1.724 x 10^-8 = 0.000010344 ohm square meters. 

The next step is to calculate the wire’s cross-sectional area. This is done by dividing our answer by our target resistance.

0.000010344/1.71 = 0.00000604912 as the cross sectional area. 

To calculate the wire’s radius in meters, we will first have to divide our above answer by pi and then square root it.

0.00000604912/3.142 = 0.00000192647 meters.

The next step is to find the square root of the above meters in order to find the radius. This will give us an answer of 0.00138797414.

We will then convert the radius into inches by multiplying it by 39.37.

0.00138797414 x 39.37 = 0.05464454215 inches. 

This radius then needs to be multiplied by 2 in order to get the diameter of the wire. This will give us a diameter of 0.11 inches.

This will approximately be a wire size of 9 AWG. 

So, it definitely is possible for a 200-watt solar panel gauge wire to be calculated manually, but it is extremely tedious, time-consuming, and leaves a lot of space for human error to occur, which is why we don’t recommend it. 

Using a Solar Wire Size Calculator to Determine Gauge Wire

If we use the same parameters and solar panel that we did in the manual calculation and insert it into an online wire size calculator, the gauge wire we get is between 4/0 AWG and 4 AWG, depending on the percentage of acceptable voltage loss. 

This is a massive difference from what was calculated above. And even though all the steps were correctly and thoroughly followed, it still gave us a very different result. 

A reason for this may be that we can’t factor an acceptable percent of voltage drop into our manual equation. We will touch on what exactly voltage drop is later, but it is a very important aspect to factor in.

Again adding on to the reasons why we prefer to calculate gauge wire through a wire size calculator. It ends up being much more accurate. 

Why it is So Important to Have the Correctly Sized

The reason that the size of the wire, in terms of length and gauge, is so important is because of the resistance they can both either cause or avoid. 

As we mentioned earlier, a smaller diameter leads to more resistance being created, which isn’t always ideal. 

Similarly, the length of the wire can also influence the resistance to the flow of current that is created. A wire that is longer will create more resistance to flow than a shorter wire with the same size diameter will. 

The Reason Why You Want to Minimize the Resistance to the Flow of Current that is Created

There are two main reasons why we want to create as little resistance to the flow of current as possible. 

The first being that if the wire is incorrectly sized, more resistance than what the wire can handle will be created. This large amount of resistance can lead to a voltage drop through the wire and can end up causing a huge amount of power to be lost from your system. 

A loss of power from your solar array could end up costing you quite a bit of money, and will also drastically decrease the performance of your system, and will make it far from optimal. 

The second reason is that an undersized wire can be a safety hazard and end up being very dangerous to those around it.

If your wires are sized incorrectly, especially if they are too small because you wanted to go for a cheaper option, they can end up overheating and creating a fire.

The fire is not only a danger to your solar system, which it could end up destroying but also to you and your family if it ends up spreading to your house or your RV. 

It is also something that can be avoided if you take the time to correctly size your wire and shows just how important it is to do so. 

What is Voltage Drop and Why Does it Matter?

Earlier on we mentioned “voltage drop” and that your wire can lose electricity.

Basically, what the voltage drop is is how much voltage is lost along the wire due to the resistance that is created. 

Some sort of voltage drop is inevitable, as there will always be a bit of resistance that is created, there’s no getting away from that. 

But, you can control how much resistance is created, and, as a result, how much voltage drop occurs. 

If a wire is undersized, and a lot of resistance is created, the resulting voltage drop can be massive.

You preferably want to try and avoid this, as it can lead to a large amount of electricity that is lost, and if you are trying to live off-grid, this is the last thing that you want to happen.

It is especially important to work out the voltage drop on wires that are 50 feet and longer. We recommend trying to keep the voltage drop below 3 - 5% if possible, as this will allow for the most optimal performance of the solar system.

Final Thoughts 

If we can offer any advice, it would be not to neglect the wire sizing for your solar panel, as you can see how crucial it is to the running of your solar array. 

If you do, it can end up costing you a lot of money, as well as endangering your safety. 

Another tip we have to offer is that you should make use of a 200-watt solar panel wiring diagram to see how many wires you need between each element and work out the wire gauge and length for each individual wire.

Don’t make your wire longer or smaller than it needs to be.

The Ultimate Solar + Storage Blueprint (Mini Course)

Struggling to understand how solar + storage systems actually work? Looking to build or buy your own solar power system one day but not sure what you need? Just looking to learn more about solar, batteries and electricity?

Join 15,000+ solar enthusiasts breaking free from their energy dependence with this short step-by-step video course that will make you a solar + storage expert. Start your journey to energy independence today.

Learn More Now

Who is ShopSolar.com?

ShopSolar.com is the #1 digital platform that enables consumers & businesses to source and purchase complete solar + storage solutions direct, saving you thousands in time, energy and money! With over 40,000+ happy customers, we’re on a mission to make solar simple, transparent and affordable.

Did you find our blog helpful? Then consider checking:

• Top 4 Portable Solar Panels
• 300 Watt Solar Panels
• 500 Watt Solar Panel System
• DIY Solar Panel System Installation Guide
• 1000 Watt Solar Panel Systems
• What Equipment You Need for a Complete Solar Panel System?
• 60-Cell vs 72-Cell Solar Panels
• How Long Do Solar Panels Last?
• Top 4 Grid-Tie Inverters Definitive Buyer's Guide