Confused about which wire gauge (AWG) you need to build a solar array? Unsurprisingly, different solar array sizes require different size wires. More specifically, the greater the current (amps) produced by the total solar array, the thicker the wires you will need.
These are the wires sizes you’ll need based on your solar array’s current (A) output.
- 0 to 10A = 14 AWG wire
- 10 to 20A = 12 AWG wire
- 20 to 30A = 10 AWG wire
- 30 to 40A = 8 AWG wire
- 40 to 50A = 6 AWG wire
But how do you figure out the maximum current (Amps) your solar array can produce?
This solar panel wire size guide will show you how to identify your solar array’s maximum current production and show you EXACTLY which wire gauge size you need to DIY your solar panel system.
You Should Know: Two Wiring Sections To Account For...
In every solar system, there are two sections of wires you need to account for. The first are the wires going from the solar panels to the charge controller. And the second section is the wires from the charge controller to the batteries. Depending on the solar array size and configuration, the wires in these two sections can either be the same size or completely different.
The graphic below illustrates these two sections of wires.
Why is it possible for the wire sizes in these two sections to be different? This is because the solar charge controller will adjust the amps and volts that it receives from the solar panels before sending the power to the batteries. And there can be situations where the solar charge controller will increase the amperage of the power from the solar panels to better charge the batteries. So if you simply use the same size wire for both wiring sections, there is a chance that the charge controller will be delivering more current (amps) through a wire that is too thin. This is a fire hazard.
In this post, we provide a 6-step process to help you properly size and purchase the ideal wire gauge for each section for your solar system.
In summary, the six steps are:
- Finalize solar array size – The total wattage is dependent on your estimated energy consumption. The more more energy you require to power your camper, the more solar you’ll need.
- Decide series vs. parallel wiring – This is only required if you have multiple solar panels to be connected together.
- Calculate array’s maximum potential amps – This is the theoretical maximum amount of current that your solar array can produce and send through the wires.
- Select wires for section 1 – The size of these wires is dependent on the max potential amps produced by the solar array.
- Calculate ideal charge controller size – This is the “amp rating” of the controller.
- Select wires for section 2 – The size of these wires is dependent on the charge controller’s amp rating.
Best Quality Wires: In this post, we only recommend pure copper, stranded wires for the best results. Many cheaper wires on the market are copper-clad aluminum (CCA), but CCA wires cannot safely conduct the same amount of amps (A) that pure copper wires can.
Confused where to start with DIY solar? Check out our comprehensive camper van solar system guide to start from the very beginning.
Step 1:
Finalize Solar Array Size
Deciding the total wattage (W) of your solar array is the first step to calculating the ideal wire size you will need. In many cases (but not all), the larger the solar array the more amps that are produced and thus the thicker the wire you will need.
Just as important, once you calculated your ideal solar array size, you must decide how many panels you will use. For example, if you decided you need 300W of solar, you could either get three 100W solar panels or two 150W solar panels. In our opinion, the fewer number of solar panels, the better.
If you still haven’t finalized your camper van’s solar array size, you should do this now before moving on. Check out our solar array sizing guide to calculate the total wattage you need for van life.
Example: After estimating our daily energy usage, we decided to purchase two 180W solar panels for our camper van. So our total solar array wattage is 360W.
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Step 2:
Decide Series vs. Parallel Wiring
After finalizing the solar array size and the number of panels you will buy, you must decide whether you will be wiring your multiple solar panels in series or in parallel. Each wiring style comes with their pros and cons. And if you are still not sure which wiring method to choose, read our series vs. parallel post to learn more.
This is a critical step because the solar panel connection method you choose can greatly affect the solar wire size you will ultimately need.
In short, solar panels that are wired in series produce fewer amps than solar panels that are connected in parallel. Therefore, panels wired in parallel tend to require thicker wires in order to safely transmit a higher amperage.
Step 3:
Calculate Max Amps Of Solar Array
At this stage you should already know the following three pieces of information regarding your solar system.
- Total wattage
- How many solar panels
- Series or parallel wiring
Now you’re ready to calculate the maximum amount of current (amps) that the solar array can produce.
In order to calculate the maximum amps (current) produced by the solar array, you’ll need to first know the amps produced by one of your panels. This is easy since each solar panel comes with a specifications list, like in the image below. You can find this list either on the backside of the solar panel or on the panel’s online product page, like on Amazon.
Simply locate the operating current or Imp(A) value to find the max amps produced by that single panel.
If you are only using one panel for your solar build, then the listed operating current on that single panel is the max amps produced by your solar system.
If you have multiple solar panels, choose from the below information based on whether your panels are wired in series or parallel.
Series Wiring
When wiring multiple solar panels in series, the maximum amperage produced by the entire array is equal to the amperage produced by just one of the panels. This is because when wiring in series, the amps of each panel DO NOT add up.
The volts (V) of each panel add up, but not the amps.
Example: If you have three solar panels wired in parallel and the operating current of one of the panels is 7A. Then the maximum amps produced by the total solar array will remain 7A.
Parallel Wiring
When wiring multiple solar panels in parallel, the maximum amperage produced by the entire array is equal to the SUM of the amps produced by each individual panels.
Example: We have two 180W solar panels wired in parallel. The max amps produced by one panel is 11.20A. To figure out the max amps of the total array, find the sum of 11.20A + 11.20A (or 11.20A x 2). Therefore, the max amps produced by the array is 22.40A.
By the end of this step, you should know the maximum amps that your solar array can produce.
Step 4:
Round Up The Max Amps And Buy Wires
Take the max amps produced by your solar array and use the table below to locate the ideal wire size for your system.
The wires we recommend in the below table are the highest quality, pure copper, marine-grade wires. These wires outperform minimum testing standards and you can trust that they will safely transmit the current (amps) produced by your solar array. As these wires are marine-grade, they are also resilient against UV light, salt water, and corrosion.
Make sure to pick up a set of RED & BLACK wires for your solar wiring project.
Max Amps | Wire Size | Buy |
0-10A | 14AWG* | |
10-20A | 12AWG* | |
20-30A | 10AWG | |
30-40A | 8AWG | |
40-55A | 6AWG |
* Note: Though 14 and 12 AWG wires would work in these instances, we recommend using a minimum of 10 AWG wire to take into account voltage drop across long wire runs and extended current flow times.
Example: Since our 2x180W solar array produces a maximum of 22.40A. Therefore, 10AWG wires are the perfect size for section one of our solar array wiring.
Section 1 Summary...
In summary, in order to calculate the best wire size to connect your solar panels to the charge controller, you will need to know the total wattage of your solar array as well as whether you are connecting the panels in series or parallel.
Once you know this information, you can calculate the maximum amps produced by your solar array, which will help you properly size section 1 of your solar wires.
Step 5:
Determine Amp Rating For Your Charge Controller
At this point, you have already identified the wire size you need to connect the solar panels to the solar charge controller. Now you’re ready to determine the wire size you need to connect the solar charge controller to the batteries.
To begin calculating the solar wires you need for section 2, you need to know the “amp rating” of your specific solar charge controller. The amp rating is the maximum amount of amps that the charge controller can output to the batteries.
If you already have your charge controller, skip to Step 6.
If you need help selecting the right size charge controller for your solar array, simply divide the total wattage of your solar array by 12. Then, round up the result to the nearest 10. The final number you get is the amp rating of the solar charge controller you need to buy.
Example: The total wattage of our 2x180W solar array is 360W. Dividing 360W by 12 gives us 30. We won't need to round up as we are already at a round number. Therefore, a 30A charge controller is ideal for our needs.
Below is a table to help you locate a recommended charge controller based on amp-rating you require. There is a wide range of solar charge controllers you could buy. But make sure you are getting an “MPPT” controller, and not a “PWM.
Rounded Up Amps | Charge Controller |
15A | |
20A | |
30A | |
40A | |
50A |
Step 6:
Determine Wire Size Between Solar Charge Controller & Batteries
The wire size needed to connect the charge controller to the batteries is determined by the charge controller’s amp-rating. For example, if your charge controller is rated for 30-Amps, then you need to select a wire that can safely handle 30-Amps of current.
In the table below, you can find your charge controller’s amp rating and see which size solar wire we recommend.
Charge Controller (Amp Rating) | Wire Size | Buy |
15A | 14AWG* | |
20A | 12AWG* | |
30A | 10AWG | |
40A | 8AWG | |
50A | 6AWG |
* Note: Though 14 and 12 AWG wires would work in these instances, we recommend using a minimum of 10 AWG for added safety due to extended current flow times.
Section 2 Summary
The below diagram shows a summary of what information you need to know in order to find the best solar wire size to connect the charge controller to the batteries.
Summary:
Wiring The Solar System Together
The below diagram is a summary showing you what wire sizes you’ll need to connect the solar panels to the charge controller and then subsequently to the leisure batteries.
Now that you’ve selected your solar wires, you might be ready to start wiring everything together. If that’s the case, check out our epic solar system wiring guide for a step-by-step installation tutorial.
Or download our free solar wiring eBook to save the information for a later date.
Download our eBooks for useful electrical, solar & plumbing diagrams. They are completely FREE.
Are “Marine Grade” Wires Worth It?
In general, we’re not super picky about the quality of our electrical wires.
Wire is wire.
We’re also building a modest camper van electrical system, not some high-tech skyscraper.
But because parts of these wires will be exposed to the elements on the roof, we think upgrading to “marine-grade” wires is a smart choice.
What Does "Marine Grade" Mean?
The standard of “marine-grade” refers to the wire’s ability to hold up against natural elements such as harsh rain, wind, and saltwater corrosion.
Therefore, if a marine-grade wire is good enough to survive a rough storm out on the open waters, it’s good enough for the roof of your van.
- 25 feet of red 10 AWG marine grade wire
- Water, corrosion, & UV resistant, perfect for rooftop setting
- Exceeds all UL 1426 standards
- Be sure to pick up 25 additional feet of black wire
Interested In The MOST Efficient (9BB) Solar Panels?
“9BB” solar panels are the next big thing in the solar panel industry. Read our 9BB solar panel post to learn why these panels are more efficient AND have a longer usable life than traditional solar panels.
Get exclusive discount on solar, power station & 12v fridge from BougeRV!
Was This Solar Article Helpful? We have other posts dedicated to help you install a camper van solar system. Check out the guide for more great RV solar content!
Final Thoughts: Proper Wire Size Is About Safety
The biggest consideration one should think about when selecting their solar panel wire size is safety.
If an electric wire cannot safely handle the current fed through it (whether in normal operations or in abnormal overcurrent situations) a fire can happen, which is dangerous to both you and your camper van.
That’s why it’s critical to select the best solar wire size for your array.
If you happen to be connecting your solar panels in parallel, consider reading our solar fuse guidelines. Fuses also play an essential role in keeping your solar PV system safe.
Happy building!
Appendix 1: Technical Solar Wire Size Calculation
If you’re interested to learn WHY you need a certain solar panel wire size for your solar array, the information in this appendix is for you.
The #1 factor that determines the size of the wire used for a solar system is the maximum instantaneous amps that can ‘potentially’ flow through that wire. The more amps, the thicker the wire size you need in order to safely transmit those amps.
The maximum potential amps is determined by both the specific panel’s operating current AND whether the solar array is wired in series or parallel.
So in order to calculate which wire size you need, you’ll need to know 3 things:
- 1. Amp-ratings for electric wires
- 2. Max amps produced by solar array
- 3. Round up to get wire size
1. Amp-Ratings For Each Solar Wire Size
Refer to below table for electric wire amp-ratings. This table is according to the National Electric Code Table 310-16.
Table 1.2 - Wire Size To Amp Rating
| Wire Size | Amp Ratings |
|---|---|
| 14AWG* | 20A |
| 12AWG | 25A |
| 10AWG | 30A |
| 8AWG | 40A |
| 6AWG** | 55A |
* Though you may find your solar system ‘qualifies’ for 14AWG wire, 12AWG should be the minimum wire size for your system.
**Finding components to fit a solar wiring project build for 6AWG wire is difficult. Try to limit your maximum wire size to 8AWG.
Good to know!
Wires of different quality may have different amp ratings, even though the wires may be the same thickness. To be conservative, we refer to the lowest amp rating for each wire gauge. But the solar wires we recommend below are ‘marine-grade’ and are actually rated for slightly more amps than the above table. But better to be safe!
2. Calculate Max Amps Produced By Solar Array
To calculate this, find the ‘operating current’ of the specific solar panel you will be using. This information is usually on a sticker label stuck on the backside of the solar panel.
If you don’t have the panels yet, you can usually find this information on the panel’s e-commerce page. Below is the panel rating specifications of our 180w solar panels.
Once you know your panel’s operating current, you can calculate your total solar array’s maximum potential amps based on whether your solar array is wired in series or parallel.
Haven’t decided how to wire your panels together? Check out our series vs. parallel solar panel wiring post to learn more.
If your panels are wired in parallel, the max possible amps produced is equal to the sum of each of the panel’s operating current. So if you had three of the above 180w panels wired in parallel, the max amps produced would be 33.6amps (11.2A + 11.2A + 11.2A).
If your panels are wired in series, the max possible amps produced is equal to the operating current of only one of your panels. That is because the amps of each panel are NOT added together in series connections. So if you had three of the above 180w panels wired in series, the max amps produced would only be 11.2amps.
3. Round Up To Get Wire Size
Once you’ve calculated your solar array’s maximum produced amps, round up to the nearest 10 to get the amp-rating of the solar wire you’ll need. Refer to the table below to find the amp-rating of each wire size.
Example: If your solar array can produce a maximum of 33.6amps, rounding up to the nearest 10 would give you 40amps. So you would need an 8AWG wire to connect your panels to your solar charge controller since 8AWG wire has an amp-rating of 40amps.
Table 1.3 - Amp Rating To Wire Size
Rounded Up Amps | AWG Wire Size | Buy Wire Size |
10 | 12AWG* | |
20 | 12AWG* | |
30 | 10AWG | |
40 | 8AWG | |
55 | 6AWG |
* 12AWG is the absolute smallest wire size you should be using. But we recommend upgrading to 10AWG, even if you are running a smaller solar system.
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