Understanding the basics without the engineering degree
If you've never worked with electrical systems before, the terminology can be overwhelming. Here's a plain-English breakdown of what you actually need to know.
Stores electrical energy - like a tank you fill up and drain as you use devices.
Convert sunlight into electricity to charge your batteries while off-grid.
Regulates power from solar panels so they don't overcharge or damage your batteries.
Charges your house battery from your vehicle's alternator while driving.
Converts 12V battery power into 120V household power for regular appliances.
Cut power if too much current flows - they prevent fires.
Tracks power in and out of your battery - like a fuel gauge.
The water pipe analogy works well here:
The "push" that moves electricity through wires. In a van: 12V (battery) or 120V (household, via inverter).
How much electricity is flowing. A phone charger draws 1-2 amps; an air conditioner draws 100+.
Watts = Volts × Amps. Same device, same watts, but voltage changes the amps:
1200W cooktop on 12V = 100 amps (needs huge wires)
1200W cooktop on 120V = 10 amps (normal wires)
Battery capacity. A 200Ah battery at 12V holds 2400Wh of energy (200 × 12 = 2400). This tells you how long you can run things.
At lower voltages, the same power needs more current. This is why 12V wires need to be much thicker than 120V wires.
Measured in AWG (American Wire Gauge) - confusingly, smaller numbers = thicker wire. Wire that's too thin for its current will overheat, waste energy, and in the worst case start a fire.
Rule of thumb: When in doubt, go thicker. Longer runs also need thicker wire - use a voltage drop calculator for each circuit. The cost difference is minimal compared to redoing your wiring.
Your van will have both 12V DC (battery power) and 120V AC (household power via inverter).
LED lights, 12V fridge, diesel heater, water pump, fans
Kitchen appliances, power tools, laptop chargers
Pro tip: Use 12V devices when possible to avoid inverter losses. A 12V fridge is more efficient than a 120V fridge through an inverter. For laptops and phones, just accept the loss.
12V is safe to touch. 120V AC (from your inverter) can be fatal. Always turn off power before working on circuits, use proper connections (no exposed wire), and ground your inverter properly.
The most common DIY mistake. Too-thin wire overheats and can start fires.
Every circuit needs a fuse. They're cheap insurance against fires.
Lithium batteries can deliver hundreds of amps instantly if short-circuited.
Thousands of people with zero electrical experience have successfully wired their vans. It takes patience, attention to detail, and a willingness to learn. If you're not confident, have someone check your work or consider a power station instead.