Campervan Electrics: The Complete Beginner's Guide

Campervan Electrics Explained: Two Systems, One Van

Campervan electrics have a reputation for being the scariest part of a van conversion, and it's not entirely undeserved — get the wiring wrong and the consequences range from flat leisure batteries to an electrical fire. But the underlying logic of a campervan electrical system is simpler than most beginner's guides make it look.

Every camper, from a weekend Vivaro to a full-time off-grid Sprinter, runs on some combination of two separate systems: a 12V DC system fed by leisure batteries, and a 240V mains system fed by campsite hook-up or an inverter. Once you understand what each side does, every other component — chargers, solar panels, fuse boxes, control panels — slots into place.

This guide walks through the complete campervan electrical system piece by piece: 12V and 240V, battery choices, charging, solar power, inverters, wiring safety, and the honest answer to whether you should build it yourself, buy a kit, or pay a professional.

12V vs 240V: What's the Difference?

The 12V system is the heart of van electrics. It runs directly off your leisure batteries and powers everything designed for life on the road: LED lighting, the water pump, a compressor fridge, USB sockets, a diesel heater, and the control panel that monitors it all. 12V DC appliances are efficient, safe to work on at low voltage, and keep running whether or not you're plugged in.

The 240V system (technically 230V AC in the UK, though everyone calls it 240V) is the same mains power your house uses. It powers domestic appliances — kettles, induction hobs, laptop chargers, hairdryers — and it comes from one of two places: a campsite hook-up post, or an inverter converting battery power to mains.

A simple van electrical system can be 12V only, and plenty of happy vanlifers never fit a 240V side at all. Most conversions end up with both: 12V for the everyday essentials, 240V mains for the power-hungry extras.

Leisure Batteries: Lead-Acid vs Lithium

Leisure batteries store the energy your van runs on, and battery capacities are measured in amp-hours (Ah). A single 100Ah battery is the classic starting point for a weekender.

Lead-acid (including AGM) is the traditional choice. It's cheap upfront and well understood, but it has real limitations: you can only routinely use around half the rated capacity without shortening its life, it's heavy, and it tolerates fewer charge cycles. For a van that spends most nights on hook-up, none of that matters much — AGM remains a perfectly sensible buy.

Lithium (LiFePO4) costs considerably more upfront but gives you nearly all of its rated capacity, weighs roughly half as much, charges faster, and lasts many times more cycles. Over years of heavy off-grid camping, the cost per usable amp-hour often works out cheaper than lead-acid.

The honest trade-off: if you camp occasionally and mostly use campsites, lithium is a luxury. If you plan to live or work from the van off-grid, lithium is usually the right call — but it needs a charging setup designed for it, which leads to the next section.

Charging on the Move: Split Charge vs DC-DC Chargers

Your engine's alternator is a free charging source every time you drive, and there are two ways to tap it.

A split charge relay simply connects the leisure battery to the starter battery once the engine is running. It's cheap and reliable, and on older vans paired with a lead-acid battery it still works fine.

A DC-DC charger (also called a B2B or battery-to-battery charger) is an intelligent device that takes the alternator's output and delivers a proper multi-stage charge at a controlled rate. It matters for two reasons. First, most modern vans have smart alternators that vary their voltage to save fuel, which confuses a basic relay. Second, lithium batteries need the correct charging profile — a plain relay can undercharge them or overwork the alternator.

The practical rule: older van plus AGM battery, a split charge relay is fine. Modern van, or any lithium setup, fit a dc to dc charger. It's the default recommendation for a reason.

Solar Power: Free Charging When Parked

Solar panels are what turn a campervan into a genuinely off-grid campervan. A panel on the roof feeds a solar charge controller, which regulates the power into your batteries. MPPT controllers are noticeably more efficient than the cheaper PWM type and are worth the extra money in almost every build — Victron's SmartSolar MPPT range is the one you'll see recommended most often in the UK van conversion community.

Sizing the solar array is a balancing act between roof space, budget and consumption. As a rough guide, 100W solar keeps a battery topped up between trips, while 200–400W supports proper off-grid camping with a fridge running.

Solar deserves more depth than one section can give it — panel types, wiring, controller sizing and realistic UK yields are all covered in our full campervan solar panel guide.

Inverters: Mains Power From Your Batteries

An inverter converts 12V DC from the batteries into 230V AC, letting you run mains appliances without hook-up. They're sized in watts: 300–500W handles laptop chargers and small electronics, while 1,000–3,000W is needed for kettles, toasters or induction hobs.

Two warnings. Buy a pure sine wave inverter — cheaper modified sine wave units can damage sensitive electronics. And be realistic about consumption: a 2,000W kettle draws well over 150 amps from a 12V battery bank, which will flatten a single 100Ah lead-acid battery in minutes. Big inverter loads really only make sense with a lithium bank behind them. Combined units such as the Victron MultiPlus pair an inverter with a mains charger in one box, which simplifies power management in bigger builds.

Hook-Up and Shore Power

Campsite hook-up (shore power) brings 240V mains into the van through a dedicated inlet socket. Done properly, the incoming supply feeds a consumer unit — a small version of your household fuse board — containing an RCD and circuit breakers, which then feeds your mains sockets and a battery charger to replenish the leisure batteries while you're pitched.

This is the part of campervan electrics most like domestic wiring, and it's the part where mistakes are least forgivable. Mains voltage in a metal box on wheels demands proper earthing, correct polarity and RCD protection — no shortcuts.

Fuse Boxes, Cable Sizes and Wiring Safety

Every single 12V circuit should run through a fuse or breaker sized to protect its cable — the fuse is there to stop the wiring overheating, not to protect the appliance. A central fuse box keeps the electrical setup tidy and makes faults easy to trace.

Cable sizes matter more than beginners expect. At 12V, currents are high and undersized cable causes voltage drop at best and overheated insulation at worst. Cable should be sized for the current it carries and the length of the run, and every battery connection needs a main fuse close to the terminal.

Before buying a single component, draw a wiring diagram: every appliance, its wattage and amp draw, cable runs and fuse ratings. An hour spent on the diagram saves days of rework — and it's the document any professional will ask for if you later want your setup checked or upgraded.

Kits vs Custom vs Professional Install

Wiring kits bundle pre-sized cable, fuses, a distribution board and a diagram for a defined setup. For a simple van electrical system — lights, pump, USB, fridge, split charge — electrical kits take most of the guesswork out and are a genuinely good route for a first van build.

Custom design makes sense once your needs outgrow the standard kit: lithium banks, large solar, big inverters, or unusual layouts. You (or your installer) spec every component around a power audit of your actual usage.

Professional installation costs more but buys design experience, tidy workmanship, and accountability if something fails. Many DIY converters split the difference: they run cables and mount hardware themselves, then have a professional design, connect and test the system.

When You Need a Professional

Here's the honest position. There is no law preventing you from wiring your own 12V system, and thousands of self-builders do it safely every year. The 240V side is different in practice: mains work in a vehicle should be installed and tested to BS 7671 (the UK wiring regulations) by a competent person, and insurers, habitation-check engineers and future buyers increasingly expect paperwork proving it.

Use a professional when any of these apply: you're fitting a mains hook-up system, you're installing a large inverter or lithium bank, you can't confidently read a wiring diagram, or your insurer asks for evidence of a professional install. Electrical faults are one of the more common causes of vehicle fires — this is the wrong place for optimistic improvisation.

What Campervan Electrics Cost

Rough UK cost bands for the whole electrical side of a van conversion, for parts:

Professional design and installation adds labour on top — often £1,000–£2,500 depending on complexity, and more for large bespoke systems. If a quote looks dramatically cheaper than these bands, ask exactly what's been left out.

Frequently Asked Questions

What electrics do you need in a campervan?

At minimum: a leisure battery, a way to charge it (split charge or DC-DC charger), a fused distribution board, LED lighting and USB sockets. Most campers add a 12V fridge, water pump and heater controls, and many fit solar panels, an inverter or mains hook-up on top of that core setup.

How much do campervan electrics cost?

For parts, a basic 12V setup costs roughly £400–£1,000, a mid-range off-grid system £1,500–£3,500, and a full lithium and solar installation £3,000–£6,000. Professional installation typically adds £1,000–£2,500 in labour depending on the complexity of the system and the van.

What is the best electrical system for a campervan?

There's no single best system — it depends on how you camp. Campsite users are well served by AGM batteries and hook-up. Regular off-grid campers should prioritise lithium batteries, a DC-DC charger and 200W+ of solar. Size the system from a power audit of your actual appliances, not guesswork.

What cable is needed for campervan electrics?

Cable must be sized for the current it carries and the length of the run, because 12V systems draw high currents and suffer voltage drop over distance. Thin accessory circuits need modest cable; inverter and battery cables must be much heavier. Every cable needs a fuse rated to protect it.

Can I install campervan electrics myself?

Yes for the 12V side — self-installation is legal and common, provided every circuit is properly fused and cables are correctly sized. The 240V hook-up side should be installed and tested to BS 7671 by a competent person, and insurers increasingly ask for evidence of professional work.