Confused about which wire gauge (AWG) you need to build your solar array? This solar panel wire size guide will teach you EXACTLY what size wires you will need to DIY a solar panel system.
Using too thin a wire is a potential fire hazard. But selecting too thick a wire provides no tangible benefit and just wastes your money.
By the end of this post, you’ll know exactly which wire size you need to build your solar panel system and the justification for why.
So if you’re ready, let’s get to it!
Not what you need? Check out our van life “Solar System” category page for more similar content.
Two Sections To Look At When Calculating Solar Wire Size
When wiring a photovoltaic system together, there are two sections to consider when calculating solar panel wire size.
- 1: Solar panels to charge controller
- 2: Charge controller to battery
In the wiring diagram below, we illustrate where these two sections are located.
The two factors that determine solar panel wire size in these two sections are:
- 1: The array's total wattage
- 2: Wire style (i.e. series vs. parallel)
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Section 1:
Calculate Wire Size From Panels To Charge Controller
The solar wire size you need to connect your solar panels to the charge controller is determined by the total amps produced by the array.
Follow our simple table below to find your ‘section 1‘ solar wire size, based on your total array wattage.
Important: You first need to decide whether your solar array will be wired in series or parallel.
Wire Sizing Chart (For Section 1)
Solar Array Size (Total Watts) | Wire Size (AWG) | Where To Buy | |
Panels Connected In Series | |||
0-200W | 12 | ||
200-800W | 10 | ||
Panels Connected In Parallel | |||
0-200W | 12 | ||
200-440W | 10 | ||
440-550W | 8 | ||
550-800W* | 6 | ||
*If building a solar array this large, consider wiring in series, NOT parallel. This is a safer system (less amps) and components are easier & cheaper to get.
Note: If you are interested to learn the technical (and complicated) details about wire sizing, check out Appendix 1 at the bottom of this post.
Section 2:
Calculate Wire Size From Charge Controller To Batteries
The ideal solar wire size between the charge controller and the batteries is dependent on the amp-rating of your solar charge controller. That’s because the amp-rating of the charge controller is the MAX amount of amps that the controller can send to the batteries.
Example:
If you have 30A rated controller but the solar wire connecting it to the batteries is only rated for 20A, you have a potential fire hazard.
And if the wire is rated for more than 30A, then that’s simply overkill and a waste of money.
The amp-rating of the charge controller is dependent on your total solar array’s wattage. Therefore, the order should be:
- 1st: Decide solar array size
- 2nd: Calculate charge controller amp-rating
- 3rd: Determine section 2 wire size
Assuming you already calculated the total wattage of your solar array, the next step is to calculate the ideal charge controller amp-rating. You can do this by referring to the table below based on the total wattage of your solar array.
Charge Controller Sizing Chart
Solar Array Size (Total Watts) | Charge Controller (Amp Rating) | Buy Charge Controller |
0-200W | 15A | |
200-260W | 20A | |
260-400W | 30A | |
400-520W | 40A | |
520-650W | 50A | |
650-800W | 60A |
Confused? Read our post to learn what a solar charge controller is and why you need one.
Once you know the amp-rating of your charge controller, you can now determine the correct solar wire size to connect the controller to your batteries.
Solar Wire Sizing Guide (Section 2)
Charge Controller (Amp Rating) | Wire Size (AWG) | Buy Wire |
15A | 12AWG* | |
20A | 12AWG* | |
30A | 10AWG | |
40A | 8AWG | |
50A | 6AWG | |
60A | 4AWG |
*Though you could use 12AWG, we recommend a minimum of 10AWG.
Example: If you need a 30A solar charge controller, then you'll need a solar wire with a minimum 30A rating, which is an 10AWG wire.
Enjoyed reading? Check out our van life “Solar System” page to learn how to build your own camper van solar system.
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.
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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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