Confused about which wire gauge (AWG) you need to build a solar array? This solar panel wire size guide will teach you how to calculate EXACTLY which size wires you need to DIY a solar panel system.
In every solar system, there are two sections of wires you need to account for. The first are the wires going from the 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.
In this post, we provide a 5-step process to help you properly size and purchase the ideal wire gauge (for each section) for your solar system.
In summary, the five steps are:
- 1. Finalize solar array size
- 2. Calculate max amps of array
- 3. Round up & buy wires (set 1)
- 4. Divide array watts by 12, round up
- 5. Buy wires (set 2)
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 amounts of amps (A) that pure copper wires do.
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
The total wattage (W) of your solar array is one of the largest factors in determining the wire sizes you need for your solar system. The larger the total wattage of the array, the thicker the wires.
Therefore, before you can move on to the next steps, you must decide how large your solar array will be.
Haven’t figured that out yet? 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. So our total solar array wattage is 360W.
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Step 2:
Calculate Max Amps Of Solar Array
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 find the operating current or Imp(A) value to locate the max amps produced by that 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 more than one solar panel, then you must also decide if you are connecting your panels in series or in parallel.
If you don’t know the difference in these connection types, check out our series vs. parallel post first.
Because series connections DO NOT add the amps produced by each individual solar panel, then the total max amps produced by the array will be equal to the max amps produced by a single panel.
But because parallel connections DO add the amps produced by each individual solar panel, then the total max amps produced by the array will be equal to the sum of the max amps produced by each panel.
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, we need to multiply 11.20A x 2, because of the parallel connection. Therefore, the max amps produced by our array is 22.40A.
Step 3:
Round Up The Max Amps And Buy Wires
Take the max amps produced by your solar array and round up to the nearest 10.
Take your result and use the table below to find the correct solar wire size to connect your solar panels to the charge controller. Remember, this is only the first section of solar wires that you need to calculate.
Max Amps (Rounded Up) | Wire Size | Buy |
10A | 14AWG | |
20A | 12AWG | |
30A | 10AWG | |
40A | 8AWG | |
55A | 6AWG |
Example: Since our 2x180W solar array produces a maximum of 22.40A. Rounding up to the nearest 10 gives us 30A. 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 4:
Divide Total Solar Array By 12 & Round Up
To begin calculating the solar wires you need for section 2, 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.
Rounded Up Amps | Charge Controller |
15A | |
20A | |
30A | |
40A | |
50A |
Step 5:
Buy Solar Wires For Section 2
When wiring the charge controller to the batteries, the ideal solar wire size corresponds to the amp rating of the solar charge controller you selected in the prior step.
The amp rating of the charge controller is the maximum amps that the controller can output to the wires. That means, you can size the wires based on the rating of the charge controller.
Use the table below to locate the best wire size for your solar array.
Charge Controller (Amp Rating) | Wire Size | Buy |
15A | 14AWG | |
20A | 12AWG | |
30A | 10AWG | |
40A | 8AWG | |
50A | 6AWG |
Section 2 Summary
Summary:
Wiring The Solar System Together
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.
10AWG Stranded Wire (Marine Grade)
- Best wire size for solar arrays
- Designed to withstand harsh environments
- Built to withstand vibrations
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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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