The Complete Campervan Electrical System Guide (2025)
This is the most comprehensive guide to campervan electrical systems on the internet. Whether you're converting a Sprinter, Transit, Ducato, or Crafter — this guide covers everything from first principles to a finished, safe system built to UK and EU standards.
If you want to skip the reading and jump straight into designing your system, our free interactive calculator does all the maths for you and generates a custom wiring diagram.
Want us to design it for you?
Our free interactive calculator sizes your entire electrical system based on your specific needs. Custom wiring diagram included.
What Is a Campervan Electrical System?
A campervan electrical system is a self-contained power setup that lets you run lights, charge devices, power a fridge, and optionally run mains appliances — all independently from campsite hook-ups.
Every system follows the same pattern:
- Charging sources put energy into your battery
- Batteries store that energy
- Distribution (fuse box, wiring) routes it to where it's needed
- Appliances use it
If you're completely new to this, start with our beginner's guide to campervan electrics which explains each component in plain English.
Sizing Your System: Start with Your Usage
The single biggest mistake people make is buying components before understanding their actual power needs. Always start with a power audit.
For a detailed walkthrough of this process, see our campervan power audit guide.
Step 1: List Every Appliance
Write down everything you want to power, its wattage, and how many hours per day you'll use it.
| Appliance | Watts | Hours/Day | Daily Wh |
|---|---|---|---|
| LED Lights | 20W | 5h | 100 Wh |
| Compressor Fridge | 45W | 12h | 540 Wh |
| Phone Charging (×2) | 15W | 3h | 45 Wh |
| Laptop | 60W | 4h | 240 Wh |
| Water Pump | 60W | 0.3h | 18 Wh |
| Diesel Heater Fan | 25W | 8h | 200 Wh |
| Total | 1,143 Wh |
Step 2: Size Your Battery
Your battery needs to store enough energy for your daily usage plus a safety buffer. The formula depends on your battery type:
For AGM batteries (50% usable depth of discharge):
- 1,143 ÷ 0.5 = 2,286 Wh → 2,286 ÷ 12 = 190Ah minimum
For LiFePO4 batteries (80% usable depth of discharge):
- 1,143 ÷ 0.8 = 1,429 Wh → 1,429 ÷ 12 = 119Ah minimum
For the full breakdown on battery types and sizing, see our campervan battery guide. For specific size comparisons, check 100Ah vs 200Ah vs 300Ah.
This is exactly what our calculator does
Our free tool automates this entire calculation. You select your appliances, and it recommends the right battery size — plus solar, charger, inverter, and wire gauges. Try it now.
Step 3: Size Your Charging
You need to replace what you use each day. The three main charging sources are:
- Solar panels — your primary charging source when parked. See our campervan solar setup guide.
- DC-DC charger — charges from the alternator while driving. See our campervan charging guide.
- Shore power — charges from campsite hook-up.
For a 1,143 Wh/day system in the UK, you'd typically want 300–400W of solar plus a 30A DC-DC charger. See how many solar panels you need for the full calculation.
The Components Explained
Batteries
Your battery bank is the heart of the system. LiFePO4 (Lithium Iron Phosphate) is the standard choice for new builds in 2025 — 80% usable capacity, 3,000+ cycle life, half the weight of AGM.
For an in-depth comparison, see LiFePO4 vs AGM batteries. For product recommendations, check our best lithium batteries for campervans.
Solar Panels
Roof-mounted solar panels are the most popular charging method. Key decisions include rigid vs flexible panels, MPPT vs PWM controllers, and series vs parallel wiring. Our solar setup guide covers all of this in detail.
DC-DC Chargers
A DC-DC charger takes power from your vehicle's alternator and charges your leisure battery. If your van has a smart alternator (most Euro 6 vehicles from 2015+), you must use a DC-DC charger rather than a split charge relay. See smart alternator explained.
Inverters
An inverter converts 12V DC to 230V AC for mains appliances. You only need one if you want to run things like a microwave, induction hob, or hair dryer. See our inverters guide for full details.
Wiring & Fuses
Every wire must be correctly sized for its current load and cable length, and every wire must be protected by a correctly rated fuse. This is where safety lives. Our wiring guide covers wire gauges, fuse sizing, colour codes, and more.
Safety is not optional
Incorrectly sized wires and missing fuses are the number one cause of campervan electrical fires. Read our guide on 10 electrical mistakes that could burn your van down before you start building.
System Design: Putting It All Together
Here's how all the components connect in a typical mid-range system:
- Solar panels → MC4 cables through roof gland → MPPT charge controller
- MPPT controller → fused cable → battery positive bus bar
- DC-DC charger → fused at both ends → starter battery and leisure battery bus bar
- Battery positive bus bar → main fuse → fuse box
- Fuse box → individual circuits → 12V appliances
- Battery positive → large fuse → inverter → 230V circuits
- All negatives → negative bus bar → battery negative
- Van chassis bonded to negative bus bar
For the recommended order of connections, see campervan wiring order. For the tools you'll need, check our electrical tools list.
Choosing Your Van
Different van models have different electrical considerations — alternator types, roof space for solar, and available mounting points.
- Ford Transit electrical system guide
- Mercedes Sprinter electrical system guide
- Fiat Ducato / Peugeot Boxer guide
- VW Crafter / MAN TGE guide
Cost Overview
| System Level | Typical Cost | Best For |
|---|---|---|
| Budget | £300–£600 | Weekend vans, minimal needs |
| Mid-Range | £800–£1,500 | Most DIY converters |
| Premium | £2,000–£4,000+ | Full-time van life |
For a detailed cost breakdown by component, see how much does a campervan electrical system cost. For a comparison of what you get at each price point, check budget vs mid-range vs premium systems.
Common Questions
Wondering whether you can do it yourself or need an electrician? Unsure how long the installation takes? Planning for winter use? Comparing part-time vs full-time van life electrical needs?
We have guides for all of these. Or if you want the simplest possible system, see whether a portable power station might work for you.
What Voltage System? 12V vs 24V
Almost all campervans use 12V systems. 24V is only worth considering for very large builds with 400Ah+ battery banks. See our full comparison: 12V vs 24V campervan systems.
Off-Grid Freedom
If your goal is to never rely on hook-ups, read our dedicated guide: off-grid campervan electrical system. It covers oversizing your solar array, managing winter charging, and which appliances are practical off-grid.
Next Steps
The best way to design your specific system is to use our free interactive calculator. It walks you through every decision, sizes all your components, and generates a complete wiring diagram customised to your build.
FAQ
How long does it take to install a campervan electrical system?
For a competent DIYer, a mid-range system takes 2–4 full days. The wiring and crimping take the most time. Planning (which our calculator handles) typically takes longer than the actual installation.
Do I need 12V or 24V for my campervan?
12V is standard for almost all campervans. 24V is only worth considering for very large systems (400Ah+ batteries, 3000W+ inverters) where the reduced current means thinner cables.
Can I do this myself or do I need an electrician?
The 12V DC side is absolutely DIY-able with proper research and planning. For 230V AC circuits, we recommend having a qualified electrician at least inspect your work. Some insurance policies require this.