RV/Van Life Wire Gauge Calculator
Created by: Liam Turner
Last updated:
Determine the correct wire gauge (AWG) for 12V and 24V DC electrical circuits in your van or RV. Calculate based on current draw, distance, and acceptable voltage drop for safe and efficient wiring.
What is an RV/Van Life Wire Gauge Calculator?
An RV/Van Life Wire Gauge Calculator helps you determine the correct wire size (AWG) for 12V and 24V DC electrical circuits in your van, RV, or camper. Proper wire sizing prevents voltage drop, overheating, and electrical fires while ensuring your appliances receive adequate power.
Unlike household 120V AC wiring, low-voltage DC systems carry much higher currents for the same wattage. This means wire gauge selection is critical - undersized wires can cause significant power loss, dim lights, slow charging, and fire hazards.
Understanding DC Wire Sizing
AWG (American Wire Gauge): Smaller numbers = thicker wire = more current capacity
Voltage Drop: Power lost as heat in wire resistance, measured as percentage
Ampacity: Maximum current a wire can safely carry without overheating
Round-Trip Distance: Total wire length including return path (2× one-way distance)
Formula: AWG selection based on (Amps × Distance) ÷ (Voltage × %Drop allowed)
Frequently Asked Questions
What wire gauge do I need for a 12V system?
Wire gauge depends on current (amps) and distance. For short runs under 3 feet: 10 AWG handles 30A, 8 AWG handles 40A, 6 AWG handles 55A. For longer runs, go 1-2 sizes larger to prevent voltage drop. Battery cables often need 4-2/0 AWG depending on inverter size.
Why is wire sizing more critical in 12V systems than 120V?
12V systems carry 10x the current of 120V systems for the same wattage. A 1200W load draws 100A at 12V but only 10A at 120V. Higher current means more heat and voltage drop, requiring much thicker wires. This is why 12V runs should be kept short.
What is acceptable voltage drop for RV/van electrical?
Keep voltage drop under 3% for critical circuits (charging, inverters) and under 5% for lighting and accessories. At 12V, 3% drop means keeping above 11.64V at the load. Excessive drop wastes power as heat and can cause equipment to malfunction.
Should I use copper or aluminum wire in my van?
Always use copper for van/RV builds. Copper has better conductivity, is more flexible, and handles vibration better. Aluminum is sometimes used in larger RVs for cost savings but requires larger gauge sizes and special connectors. Stick with copper for reliability.
What's the difference between stranded and solid wire?
Always use stranded wire in mobile applications. Stranded wire is flexible, handles vibration without breaking, and is easier to route through tight spaces. Solid wire is for fixed installations like houses. Use fine-strand (marine-grade) wire for the best durability.
How do I calculate wire length for voltage drop?
Measure the total round-trip distance - from source to load AND back. A light 6 feet from the battery is actually 12 feet of wire for voltage drop calculations. This is the most common mistake in 12V wire sizing.
What wire gauge for solar panel to charge controller?
Size for the maximum solar current plus 25% safety margin. For a 400W array at 12V (about 33A max), with a 15-foot run, you'd need 8 AWG minimum for <3% drop. Higher voltage panels (24V+) can use smaller wire due to lower current.
Do I need to fuse every wire in my van electrical system?
Yes, fuse every positive wire at its source (battery, bus bar, fuse block). The fuse protects the wire, not the device. Size fuses to protect the wire's ampacity - a 10 AWG wire rated for 30A should have a 30A or smaller fuse, regardless of the load.
Sources and References
- ABYC (American Boat and Yacht Council), "E-11 AC and DC Electrical Systems on Boats"
- Blue Sea Systems, "Circuit Wizard Wire Sizing Guide", bluesea.com
- Victron Energy, "Wiring Unlimited", victronenergy.com