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How-to Choose Wire Sizes DIY Camper Van Electrical System

There are many different sizes, shapes, colors, and ratings of wires.  It’s pretty confusing.  For this blog post, I’ll teach you to size wires for a DIY Camper Electrical setup and point you in the direction of the wires I recommend. Sizing the wires for your camper solar setup can get super complicated…if you let it.  So don’t let it…

Quick note before we get started.  This is just one part of an overarching “How to Install a DIY Camper Van Electrical System” series.  If you’ve just stumbled on this article directly without seeing that, there are likely some things we’ve already covered.  If you want to check out that step by step guide, you can do that here:

Also, we have interactive solar wiring diagrams that are a complete, A to Z solution for teaching you exactly what parts go where, what size wires to use, fuse size recommendations, wire lug sizes, and all kind of other stuff to help save you time and frustration.  You can check that out here:

How to Size Wires for your Solar Setup

  • Step 1: Read the instruction manual for the item you are attempting to wire.  Seriously… most of the time it tells you exactly what size of wire and fuse to use.  Trust it.  They’ve got electrical engineers backing those numbers.
  • Step 2: Use my wiring diagrams.  I have read those numbers found from step 1 and applied them to my wiring diagrams.
  • Step 3: Figure it out yourself. Which is what we are going to talk about now.

The following chart may look familiar if you’ve already been trying to find an answer to the question”How do I size my camper van wires”.  This chart, though, is a little different.

I didn’t like most of the diagrams already out there, so I made my own.  Here’s what you do.

  • Determine how many amps will be flowing to your appliance.  Find that number in the column on the left.
  • Determine how far your appliance will be from your power source.  Find that number on the top row.
    • (not round trip… this graph accounts for that)
  • Follow the column down and the row over to the appropriate box.
  • The two numbers are the wire gauges that will work for that run of wire.
    • Green = 3% voltage drop
    • Red = 10% voltage drop.
  • Try to stay closer to the ‘green’.  Red is still fine, but only for “Less important” things such as fans, lights, usb outlets, etc.
  • Consider ‘green’ as the Ideal wire gauge.
  • Consider ‘red’ as acceptable, but really try to go for green…

DIY Camper Electrical System Cheat Sheet:

Please verify using the above guidelines, but these wires will work for most situations.

Pro Tip: Be flexible in your wire sizes, if you need 3 feet of 2ga, 4ft of 4ga, and 4 ft of 6 ga; consider using 2ga for all of it and just buy a longer section of 2 ga rather than buffet style wires.

Now that you know what size of wire to use in your DIY camper van electrical system, it’s time to learn what type and size of fuses you’ll need to make sure your system doesn’t catch on fire in case of malfunction.  Check out how to size fuses here:

Everything that you are learning here is put to use in our FREE Interactive Solar Wiring Diagrams.  If you haven’t yet, check them out as they are a complete solution for a camper van electrical system.  Check them out here:

Remember, this is just one part of a full camper van electrical educational series.  To see all of the individual guides, click here:

Finally, If you found this guide helpful, It’d truly mean the world to us if you’d share it with somebody who can use it, pin it to pinterest for later reference, or share it to a facebook group when somebody has a question about this subject.  Click the bubble in the lower right corner to subscribe to be notified of future updates and as always, leave any questions you’ve got in the comments below.


Tuesday 28th of December 2021

Using a induction cooktop and nespresso machine at the same time in combination with other 12v appliances, I expect I might use up to 500 amps at peak usage, what wire size would I need for this system between the batteries? Does the 4/0 AWG from the wiring diagram work for this?

Christopher Carlin

Tuesday 24th of August 2021

Hey Nate,

When calculating the wire size should the distance be calculated off of where the furthest power point is or off of the total footage? For example, if you are running two fans on the same circuit and one fan is 7 feet away and the other is 10, do you use 10 as the number or do you need to add in the distance between the two fans? i.e. 7 feet to fan 1 plus 6 foot run to fan 2 giving you a total distance of 13 feet?


Monday 5th of July 2021

Nate, Love your site and videos. I'm setting up my van to use a Multiplus 12|3000|120-50|120V, in the manual on page 8 it states, "0-5m use wire size 2x 50mm2 (2 positive & 2 negative cables)". An mm2 to AWG chart lists 4/0 as 120mm2, will using a single 4/0 cable meet the 2x 50mm2 spec? Thanks Richard

Andy B Medeiros

Monday 17th of May 2021

Hey Nate, Thank you so much for all the information you provide! I've purchased everything on your list except the wires from I'm just curious why you chose those instead of others I'm seeing on Amazon for a significantly lower price. Can you provide insight as to how the quality difference justifies the price.

Nate Yarbrough

Tuesday 18th of May 2021

The ones from BatteryCablesusa are a bit higher quality and you have the option of having them pre-crimp lugs onto the wires, which was a requested thing from me... but more importantly... Sellers on Amazon have struggled to keep wire in stock, which makes my parts list... less than useful. Batterycablesusa is a more reliable source.


Wednesday 28th of April 2021

My dad has a small trailer and I am trying I size everything perfect for him he just needs lighting a wather heater and water pump I just want I make sure I do it right for him especially if I do a solar to make him to make hit proud.