What Wire Sizes For Camper Van Electrics? (How To Calculate)

Using the correct wire sizes for your camper van electrical system is critical for safety. If you try to pass too much electrical current (amps) through too thin of a wire, the metal conductors can get too hot and burn away the outer insulation, which poses a dangerous fire hazard.

However, choosing the best wire sizes for your van conversion is complicated because there is no “one size fits all” solution. Different-sized electrical systems require different-sized wires. But even then, helping to size your camper van’s wires is very much doable.

This post provides a simple and safe method for sizing all your camper van’s wires. This includes the battery cables, solar panel wires, inverter wires, and more. Though you could make an itemized list of all your devices and do the required math to get your “perfect” wire size, our method requires no heavy calculations and is arguably safer. If you’re ready to learn more, let’s get to it!

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Wire Safety Theory

In the USA, wire thickness is measured in “American Wire Gauge” (AWG). The larger the AWG number, the thinner the wire. So, a 2 AWG wire is significantly bigger than a 14 AWG one. It’s counterintuitive and confusing at first.

International standard: Outside North America, the rest of the world uses square millimeters (mm²) to measure wire size. The bigger the wire, the larger the mm². It pains me as an American to say, but this makes more sense! Where convenient, we will refer to both AWG and mm².

Heat is created when electrical current – or amps (A) – passes through a wire conductor. When a wire pushes too many amps, the interior metal conductors get so hot that they melt the outer insulation, which can start a fire.

Fire = bad.

The thicker the wire, however, the more amps it can carry before the wire overheats. This is why the more amps you intend to pass through the wire, the thicker it should be (smaller AWG number or larger mm²).

To help you size your wires, you can refer to wire ampacity tables, which certify the ampacity ratings for each wire size based certain criteria, such as temperature rating and conductor material. However, these tables are confusing unless you’re an electrician and, since there are many different grades of electrical wire, these tables leave us with more questions than answers.

How We Will Size Our Camper Van Wires

We will use Windynation-branded cables for the majority of our wire recommendations. When we contacted Windynation about the ampacity ratings of their wires, we received this reply:

“Attached is our Certificate of Conformance for our cable. The ampacity is indeed continuous in open air (room temp).”

-Windynation Support Staff

Their certificate of compliance is the perfect resource because it verifies Windynation’s own wire ampacity ratings in a continuous current environment instead of relying on a generic third-party table that encompasses many different wire grades. We will refer to this certificate when recommending your van’s wire sizes.

We also like Windynation because the American-based company manufactures premium-quality pure copper wires encased in a tough EPDM rubber insulation jacket for high-temperature resistance and ultra-flexibility. Lastly, these wires are assembled in the USA, which we prefer because this gives us greater reassurance that we can trust the wire quality and their verified ampacity ratings.

Note: For wires smaller than 8 AWG, we will recommend other premium quality wires and refer to the most conservative column of the wire ampacity table for maximum safety. This will be a tad excessive, but safety for us (and for your van) is paramount.

12V System Wire Size

A camper van’s 12V system comprises five sections. Each section requires different wire sizes since we expect different amounts of electrical current to pass through these circuits. The five parts are:

• Part 1: Combining batteries
• Part 2: Batteries to bus bars
• Part 3: Bus bars to fuse panel
• Part 4: Fuse panel to 12V devices
• Part 5: Ground wire

Part 1: Combining Batteries

If you have multiple batteries, you will need to wire them together. Most websites recommend adding up the electrical current of every device in your van to determine your ideal wire size. We propose a different sizing method.

The maximum ‘potential’ current that your wires must sustain is the sum of the maximum current of your inverter (AC system) and fuse panel (DC system).

Max inverter amps + Max fuse panel amps = Max total amps

Wire Size Recommendation

And since our suggested 12V panel is rated for a maximum of 100A, we can recommend your wire size by knowing what size inverter you plan to install. In the below table, find your inverter size (first column) to determine your max amps (second column) and ideal wire size (third column).

Inverter Size1 + 12V Panel2	Max Amps	Wire Size
No Inverter + 100A	100A	2 AWG
1000W (83A) + 100A	183A	1/0 AWG
2000W (167A) + 100A	267A	2/0 AWG
3000W (250A) + 100A	350A	4/0 AWG

Table Footnotes:
1. Inverter watts/12V = Amps
2. Fuse panel specifications

Not sure what size inverter you will use? Scroll down to our inverter size calculator.

Have a 24V battery bank? Divide your inverter’s wattage rating by 24 (instead of 12) to get the correct amperage draw. Then add 100A from the 12V fuse panel (assuming you are using a voltage converter).

Example: If you have a 1000W inverter, the maximum amps the battery wires will experience will be 83A (1000W inverter @ 12V) + 100A (fuse panel) = 183A. We recommend 1/0 AWG wire, which has a max ampacity rating of 285A. This is a safe wire size recommendation.

Below are our Windynation wire gauge recommendations based on your inverter wattage rating (mm² recommendations included). Since our camper van has a 2000W inverter, we use 2/0 AWG wires to connect our batteries.

Our video below reviews EWCS 2/0 gauge wires. However, we later bought Windynation wires and discovered they are the same build and quality but are significantly cheaper.

Unsure how to attach electrical wire to the batteries? Please read our quick lug crimping tutorial (with video).

Part 2: Batteries to Bus Bars

It is best practice to wire the batteries to bus bars, which are the electrical system’s power collection and distribution centers. We will wire the two major loads (inverter and 12V fuse panel) to these bus bars. Consequently, the wires you use to make this connection must handle the same amount of amps (i.e., the same wire size) as the wires you used to connect your batteries together.

Example: In the above wiring diagram, because we used 2/0 AWG wires to connect our two batteries, we will also use 2/0 wires to connect to the bus bars.

• 2 AWG wire
• 1/0 AWG wire
• 2/0 AWG wire
• 4/0 AWG wire

That was easy!

Fuse Size Recommendation

You must install a fuse on the positive (red) wire for electrical safety. We list the ampacity ratings of the fuse you require based on the wire size you selected above. These fuses are correctly sized in accordance to Windynation’s wire ampacity table.

• 2 AWG = 150A fuse
• 1/0 AWG = 200A fuse
• 2/0 AWG = 300A fuse
• 4/0 AWG = 400A fuse

Our example: We use a 2000W inverter. So, we use a 2/0 AWG wire and protect the circuit with a 300A fuse.

Part 3: Bus Bars to 12V Fuse Panel

The next step is to connect the bus bars to the 12V fuse panel. This is straightforward because we will use Blue Sea System’s panel, and the manufacturer recommends using either 4 or 6 AWG wires. Below is a picture of the backside of the panel’s packaging, which states the product specifications and the recommended wire size.

Since we like to be conservative in our wiring sizing, we’ll go with the larger of the two size recommendations, which is 4 AWG. This makes sense since the ampacity rating of Windynation’s 4-gauge wires is 150A, and the fuse panel has a maximum operating amperage of 100A. Therefore, the panel can function without being restricted by the wire.

Our video below reviews Windynation’s 4 AWG wire. We strip away the insulation to expose the bare copper strands and explain why we recommend this wire for your build.

Circuit Breaker Size Recommendation

Blue Sea Systems recommends a maximum of a 125A fuse/breaker when wiring to the 12V fuse panel. So this 120A breaker is what we use to protect the 4 AWG wire.

Part 4: Fuse Panel to 12V Devices

This section connects the fuse panel to every 12V device (e.g., the fan, LED lights, & USB sockets). We recommend using 14 AWG wires (2.5mm²) to make these connections. Under the most conservative calculations, a 14-gauge wire is approved for up to 15A, which is 180W of power (for 12V systems). The vast majority of 12V devices won’t demand anywhere near that amount of power.

In particular, we like the 14 AWG ‘duplex’ wires from GS Power. ‘Duplex wire means two 14-gauge cores (red and black wires) are packed together inside an outer insulation sheath. These are marine-grade wires, meaning they better resist corrosion and mechanical fatigue from vibration.

Upgrade to 12 AWG?: If your wire runs are longer than 30′, we recommend upgrading to 12 AWG wire instead to combat issues with voltage drop. The longer the circuit, the more voltage is lost, which may interfere with the performance of specific devices. But in our van, we’ve never experienced this issue.

Watch our GS Power 14 AWG wire review below. We break down this product and reveal why we love this wire when connecting to each 12V device.

Part 5: Ground Wire Size

According to the National Electric Code (Article 250, Table 250.66), the ground wire’s gauge depends on the largest cable size you use in other parts of your electrical system.

Therefore, locate your ideal ground wire size based on the size of the wire you used to connect your batteries to the bus bars.

• 2 AWG wire = 8 AWG ground wire
• 1/0 AWG wire = 6 AWG ground wire
• 2/0 AWG wire = 4 AWG ground wire
• 4/0 AWG wire = 2 AWG ground wire

Example: In our van, because we use 2/0 AWG wire to connect our batteries to our bus bars, we will use 4 AWG wire for the ground connection.

For ground wire, TEMCo provides the most convenient solution (single color @ 5-foot lengths) at the most affordable price.

Inverter System Wire Size

This chapter covers the wire sizes required to install a 120V power inverter in a camper van. We separate this chapter into three parts and provide detailed diagrams for each section.

• Part 1: Inverter to batteries
• Part 2: Inverter to power outlets
• Part 3: Ground wire

Part 1: Inverter to Bus Bars

In the previous chapter, we sized the battery wires based on the inverter wattage size. Consequently, the wire size you require to connect the inverter to the bus bars will be the same as the wires you used in Part 1 and Part 2 of the 12V system.

• 1000W inverter: 1/0 AWG wire
• 2000W inverter: 2/0 AWG wire
• 3000W inverter: 4/0 AWG wire

Wire size justification: We encourage you to scroll up and revisit Part 1 of the 12V system, where we explain which wire size you should be using and why.

Fuse Sizing

You must install a fuse on the positive (red) wire for electrical safety. We list the ampacity ratings of the fuse you require based on the wire size you selected above. These fuses are correctly sized in accordance to Windynation’s wire ampacity table.

• 1/0 AWG = 200A fuse
• 2/0 AWG = 300A fuse
• 4/0 AWG = 400A fuse

Our example: We use a 2000W inverter. So, we use a 2/0 AWG wire and protect the circuit with a 300A fuse.

Part 2: Wiring the Inverter to Sockets

Every inverter has an ‘AC Out’ section, where the 120V ‘AC’ power exits the inverter and is distributed to all the van’s power outlets. This section covers the wire sizes you’ll need to make these connections.

When connecting an inverter to the power outlets, pay attention to the two different circuits of electrical wire. We’ve noted both circuits in the above diagram.

1. Feeder circuit: This circuit connects the inverter to the breaker box.
2. Branch circuit: This circuit connects the breaker box to the sockets.

Feeder Circuit

This wire is responsible for transmitting the maximum power the inverter can deliver to the main breaker box/panel. As such, the wire size for the feeder circuit depends on the wattage rating of your inverter.

When sizing the wires to the breaker, it’s important to consider the inverter’s ‘peak power,’ which is the increased maximum power production that the inverter can produce for the first few seconds on startup. The peak power is usually 2x the inverter’s rated wattage, so a 1000W inverter has a peak power production of 2000W. You can imagine that not factoring in peak power into your wire sizing can have disastrous results.

The table below recommends the wire size you’ll need (column 3) based on your selected inverter’s peak power rating. In our appendix, you can cross-reference the max amps (column 2) produced by the inverter to the wire ampacity chart.

Inverter (Peak Power)	Max Amps1 & 2	Wire Size3
1000W Inverter (2000W)	18.2A	12 AWG
2000W Inverter (4000W)	36.4A	8 AWG
3000W Inverter (6000W)	54.5A	6 AWG

Table Footnotes:
1. Max amps = peak power/120V
2. If 230V inverter, divide peak power by 230V
3. Wire size for 120V inverters. One size down for 230V

What does Victron say? On page 23 of the product manual, Victron also recommends 6 AWG wires for their 3000W inverter.

Branch Circuit

No matter the size of your 120V inverter, we recommend connecting the circuit breaker box to each power outlet with 12 AWG wires. Household outlets are rated for 15A, so 12-gauge wire (20A rating) will be sufficient to carry the electrical current safely.

Important: To ensure electrical safety, we recommend wiring each circuit breaker to only one pair of power outlets. If you plan to have two pairs of sockets in your van, plan to have two circuit breakers.

230V inverter? Follow our wire size recommendations and reduce the size by 1 to 2 levels. However, refer to a wire ampacity table to double-check.

Recommended Wire

Electrical cables for AC power are called ‘triplex wire’ because they comprise three inner wires (hot, neutral & ground) encased in an outer insulation jacket.

For 12 AWG and 8 AWG wires, we recommend Kimbluth’s marine-grade triplex wires. We use them in our camper van and are happy with the quality. For 3000W inverters, Windynation’s 6 AWG triplex wires are a great choice.

Does your 3000W inverter accommodate four wires? Some large inverters, like Victron’s 3000W inverter, have space for two ‘hot wires’ (L1 and L2). In this case, use Windynation’s 6 AWG ‘quadplex’ wires.

Part 3: Ground Wire

Following the same NEC ground chart earlier in this post, we recommend ground wire sizes based on the wire size you used to connect the inverter to the bus bars.

• 1/0 wire = 6 AWG ground wire
• 2/0 wire = 4 AWG ground wire
• 4/0 wire = 2 AWG ground wire

Solar System Wire Sizes

This section covers the wire sizes needed to build a solar system in a camper van. We divide this solar wiring section into two parts.

• Part 1: Solar panels to charge controller
• Part 2: Charge controller to bus bars

Part 1: Solar Panels to Solar Charge Controller

Correctly sizing the wires from the solar panels to the charge controller involves a two-part process:

• Part 1: Calculate the maximum current output of the solar array.
• Part 2: Multiply max current by 1.56 for NEC safety factor (NEC 690.8)

Example: Two solar panels wired in parallel, each with a short-circuit current of 11.75A, have a maximum current output of 23.5A (11.75A + 11.75A). Multiplying 23.5A by 1.56 gets us 36.7A.

If you are serious about solar wiring safety, we encourage you to read our solar wire sizing guide. It is a fantastic & detailed resource that breaks down exactly what wire sizes you need for every section of a solar system.

Below is a summary table of recommended solar wires based on the amperage figure you calculated after the 1.56 NEC safety factor.

Solar Array Amps (After 1.56x Factor)	Solar Wire Size1
30A (or less)	12 AWG
30-40A	10 AWG
40-55A	8 AWG

Table Footnotes:
1. Recommendation based on the below ampacity table.

The above wire size recommendations are based on Windynation’s USA-made wire ampacity ratings, which are UL (Underwriter Laboratories) certified.

Example: Our two 180W solar panels wired in parallel output a theoretical (1.56x safety factor) maximum of 36.7A. This means we use 10 AWG wires to connect our solar panels to the charge controller.

Solar Wire Size Recommendations

Based on the solar wire sizes above, we recommend the below Windynation solar connectors. These wires already come with MC4 connectors crimped on both ends. We prefer these wires because the jackets are UV/sunlight resistant, which is essential for solar cables placed on the vehicle’s roof.

Note: For wires longer than 20 feet, consider upgrading to one size larger to prevent voltage drop and power loss.

Part 2: Solar Charge Controller to Bus Bars

The size of the wires you’ll need to connect the solar charge controller to the bus bars depends on the charge controller’s ampacity rating. This wire size is NOT necessarily the same as the wires from the previous part, which connected the panels to the charger. This is because the charge controller will adjust the incoming voltage, which often means the amperage leaving the charger is greater than the amps entering the charger.

Charge Controller Ampacity Rating	After 1.25x NEC Factor1	Wire Size2
0-20A	25A	10 AWG3
30A	37.5A	8 AWG
40A	50A	8 AWG
50A	62.5A	6 AWG
70A	87.5A	4 AWG4

Table Footnotes:
1. NEC code 690.8(B)(1)
2. Refer to Windynation certificate ampacities unless otherwise noted
3. Refer to the general ampacity table
4. The smallest wire gauge referred to in the Victron manual

Below, you can locate the wires you’ll need based on the ampacity rating of your solar charge controller (after multiplying the 1.25 NEC safety factor). The amps are listed in the light blue fields.

In our van, we have a 30A solar charge controller—which becomes 37.5A after the 25% safety factor—and connect it to the bus bars with 8 AWG wires.

Check out our solar install guide for more specific information, including recommended parts and components. You can also download our free solar eBook.

Wire Size for Alternator (DC-DC) Charging

Wires for DC-DC chargers are tricky to size because the total circuit length—from the vehicle’s alternator to the charger and to the bus bars—can be pretty long. So, you must consider the charger’s ampacity rating and the potential for voltage drop.

OR…you can refer to the product manuals and locate the maximum allowable wire size for each DC-DC charger. For example, below is an excerpt from Victron’s product manual recommending 6 AWG for their 18 & 30A DC-DC chargers for their longest circuit lengths (5-10 meters).

Below is a table with the three most common DC-DC chargers (two Victron and one Renogy). Our recommended wire size is based on the suggested wire sizes in the product manuals, which you can reference from the table footnotes.

Manufacturer	DC-DC Charger	Wire Size
Victron	18A	6 AWG1
Victron	30A	6 AWG1
Renogy	40A	4 AWG2

Table Footnotes:
1. According to the Victron product manual
2. According to the Renogy product manual

Check out our DC-DC charger install guide for more specific information on installing a DC charger with recommended components.

Final Thoughts: Campervan Wiring Is Just the Beginning!

Thank you for making it this far in our campervan wiring post! We hope you learned about the best wire size for your van conversion.

But buying the right size wires and laying them in your van is just the first step. For more information, read our DIY van electrical guide or download one of the many free resources we provide to aid your van conversion.

If you have any questions, please comment in the below section.

Happy building!

Appendix

Inverter Size Calculator

Below is a simple calculator to help you quickly determine what inverter size and type you need without any math calculations. Just answer a few questions, and the calculator will recommend a budget and premium inverter.

Wire Ampacity Chart (Abridged)

Below is a condensed version of a standard wire ampacity chart. We only included the wire sizes relevant to this post and chose the most conservative ampacity rating (temperature rating of 60°C). For a comprehensive table, visit this wire chart.

Wire Size (AWG)	Ampacity Rating (@ 60°C)
14	15
12	20
10	30
8	40
6	55
4	70