VANPOWERCALC

Your Van Electrical System

Design your entire 12V electrical system for your van build: Solar, Batteries, Inverter and Wiring. Community approved tool.

This tool crunches all the numbers to give you a complete, safe, and balanced electrical system setup for your vanlife travels.
⚡ Expert tip
The most overlooked component in van electrical planning: the negative (ground) return path. Most builders obsess over positive fusing and ignore that every amp flowing from the battery positive must return through the negative. Use equal-gauge negative cables back to a negative busbar, and ensure that busbar has a single, clean, thick connection back to the battery negative terminal.

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Comparison table

ComponentEntry budgetMid budgetPremium budget
Battery 100-200Ah$150-300$300-500$600-900
Solar panel 100-200W$60-100$100-180$200-350
MPPT controller$30-50$50-100$100-200
Inverter 300-1000W$40-100$100-180$200-350
TOTAL$280-550$550-960$1,100-1,800

About this tool

A complete campervan electrical system is more than panels and a battery — it's a circuit design exercise that determines whether your system is safe, efficient, and expandable. Understanding the function of each component prevents the most common (and expensive) installation mistakes.

The battery bank is the heart. LiFePO4 is now the default choice for serious builds: 100Ah to 400Ah capacity at 12V, with 100% depth of discharge usable, 3000+ cycle life, and Bluetooth monitoring available on all quality units (Victron, CATL-cell brands). Size to 2× your daily consumption in Wh.

Solar panels feed the MPPT charge controller. The controller's job is converting the higher panel voltage (17-40V depending on wiring) down to battery charging voltage (14.2-14.4V for LiFePO4) with maximum efficiency. Victron SmartSolar MPPT controllers (75/15 to 250/100) are the van-life standard, with Bluetooth integration and programmable charge profiles.

The DC-DC charger from the starter battery handles driving-based charging. This is essential for modern Euro 5/6 vans with smart alternators — without it, your LiFePO4 will never fully charge from driving. Victron Orion-Tr Smart 12-12|30 (30A = 360W) is sufficient for most builds; two in parallel gives 60A for faster charging.

The distribution board ties everything together. Use a central positive busbar with individual fuse holders per circuit (not a master breaker feeding everything — that defeats the purpose of circuit protection). Each load group gets its own fuse: fridge (20A), lights (10A), USB sockets (10A), water pump (15A), inverter via its own 200A ANL. Keep 230V circuits behind an RCD if shore power is installed.

Final safety check: all cables must be rated for the maximum potential current, not just typical use. 12V cable ratings assume 12V, 1m length — for actual wire sizing, use a voltage drop calculator with your actual cable run lengths. A 3m run at 100A needs 35mm² cable to stay under 3% drop.

Why does an accurate electrical system calculator matter? The penalty for under-sizing is either constant battery anxiety (running out of power) or expensive mid-build upgrades (replacing 100Ah with 200Ah after the system is already installed, often requiring fuse and cable upgrades too). The penalty for over-sizing is wasted money: a 400Ah LiFePO4 for a weekend camper who uses 200Wh/day is €600 sitting unused 90% of time.

Calculating your system systematically: 1) List every load with watts and daily hours, 2) Sum for Wh/day, 3) Battery = Wh/day × days autonomy ÷ (system voltage × DOD%). 4) Solar = Wh/day ÷ PSH × 1.25 losses, 5) MPPT = panel watts ÷ battery voltage × 1.25. These five steps produce a specification; VanPowerCalc automates them with local PSH data for European locations built in.

Iterating on the design: once you have numbers, question each load. Is the fridge necessary? A 50L LiFePO4 cooler (30W, 360Wh/day) can be replaced with high-quality cooler bags + daily ice replenishment for weekenders — saving 400Wh/day and €300-500 in system cost. Is Starlink necessary? In France and Italy, 4G covers 95% of van destinations — Starlink's 720Wh/day overhead may not justify itself outside of deep rural northern Europe.

Frequently asked questions

What does a complete campervan electrical system include?▼
A complete system has six components: battery bank (stores energy), solar panels (primary harvest), MPPT charge controller (converts solar to usable charge), DC-DC charger (alternator charging while driving), battery charger (shore power charging), and a distribution board with fuses/circuit breakers for all loads. Optional: inverter for 230V appliances, Cerbo GX for monitoring.
What order should I wire a van electrical system?▼
Wire in this order: 1) Battery → main fuse (ANL 125A within 30cm), 2) Battery → negative busbar (common negative point), 3) DC-DC charger from starter to leisure battery, 4) Solar MPPT controller output to battery (separate circuit), 5) Distribution board from battery with individual fused circuits per load group (lights, 12V sockets, fridge, pump). 6) Inverter last — it draws highest current.
How do I calculate the main fuse size for a van electrical system?▼
Main fuse = total maximum current draw × 1.25 safety margin. A typical system: inverter 2000W (166A at 12V) + fridge 5A + lights 5A + pump 5A + DC-DC charger 5A = 186A peak theoretical maximum. Main ANL fuse should be 200A. In practice with diversity factor (not everything runs simultaneously), 150A ANL is sufficient for most van builds under 2000W inverter.
Do I need a bus bar in a van electrical system?▼
Yes — a positive and negative bus bar simplifies wiring significantly and reduces connection points where faults can occur. Every load connects to the bus bars via its own fused circuit. The bus bars connect to the battery via thick cables (35mm² minimum for 200A systems). Popular choice: Blue Sea Systems 150A bus bars with integrated fuse holders — €40 each, marine grade, proven in van builds.
Should I use 12V or 24V for my van electrical system?▼
12V for most van conversions (under 300Ah and 300W solar): all 12V accessories work directly, most components are optimized for 12V, and system complexity is lower. 24V makes sense for solar arrays over 600W (halves cable current for same power), inverters over 2000W (safer, more efficient at 24V), and builds with over 400Ah battery capacity. Sprinter-based large motorhome conversions more frequently use 24V.

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